paulo matos - Academia.edu (original) (raw)

Papers by paulo matos

Fisioterapia, 2006

Este estudio tiene como objetivo evaluar los indicadores antropométricos de las mujeres posmenopa... more Este estudio tiene como objetivo evaluar los indicadores antropométricos de las mujeres posmenopausias con edad de 45 hasta 65 años, con las diferencias fases de pérdida de la densidad ósea. La muestra fue constituida por 52 mujeres, las cuales fueron divididas en grupos de osteoporosis, formados por 23 mujeres (58,2 ± 3,3 años) y grupo de osteopenia formada por 29 mujeres (57,2 ± 6,1 años). La evaluación antropométrica obtuvo datos de la composición corporal, relación cintura-cadera (RCC), la suma de los pliegues del tronco y el índice de la masa corporal (IMC). Los procedimientos estadísticos fueron la media entre desvió-padrón y la amplitud de variación. El análisis del perfil de normalidad de las distribuciones, fue realizado por intermedio del test de Shapiro-Wilk, se utilizó el test T de medidas independientes y el test

Molecular Cancer Research, 2008

The small GTPase Rac1 can stimulate various signaling pathways that contribute to cell transforma... more The small GTPase Rac1 can stimulate various signaling pathways that contribute to cell transformation. In particular, the activation of the NFKB transcription factor initiates an antiapoptotic response and promotes cell cycle progression through increased cyclin D1 expression. As a potential oncogenic mechanism to up-regulate this pathway, the overexpression of the Rac1b splicing variant was reported in some colorectal tumors. Rac1b exists predominantly in the active GTP-bound state and selectively promotes the pathway leading to NFKB activation. Here, we studied the role of endogenous Rac1b in colorectal cancer cells. We found that depletion of Rac1b by small interfering RNAs inhibited endogenous NFKB activation and reduced cell viability to 50% within 48 hours. This reduction was due to increased apoptosis, although a reduced G 1 -S progression rate was also observed. These data show, for the first time, that colorectal cells expressing alternative spliced Rac1b also depend on Rac1b signaling to sustain their survival. (Mol Cancer Res

Biochemical and Biophysical Research Communications, 2000

Genes Chromosomes & Cancer, 2006

The MLL gene, at 11q23, undergoes chromosomal translocation with a large number of partner genes ... more The MLL gene, at 11q23, undergoes chromosomal translocation with a large number of partner genes in both acute lymphoblastic and acute myeloid leukemia (AML). We report a novel t(9;11;19)(p22;q23;p13.3) disrupting MLL in an infant AML patient. The 5′ end of MLL fused to chromosome 9 sequences on the der(11), whereas the 3′ end was translocated to chromosome 19. We developed long-distance inverse–polymerase chain reaction assays to investigate the localization of the breakpoints on der(11) and der(19). We found that intron 5 of MLL was fused to intron 5 of MLLT3 at the der(11) genomic breakpoint, resulting in a novel in-frame MLL exon 5–MLLT3 exon 6 fusion transcript. On the der(19), a novel gene annotated as FLJ10374 was disrupted by the breakpoint. Using reverse transcription–polymerase chain reaction analysis, we showed that FLJ10374 is ubiquitously expressed in human cells. Transfection of the FLJ10374 protein in different cell lines revealed that it localized exclusively to the nucleus. In serum-starved NIH-3T3 cells, the expression of FLJ10374 decreased the rate of the G1-to-S transition of the cell cycle, whereas the suppression of FLJ10374 through short interfering RNA increased cell proliferation. These results indicate that FLJ10374 negatively regulates cell cycle progression and proliferation. Thus, a single chromosomal rearrangement resulting in formation of the MLL–MLLT3 fusion gene and haplo-insufficiency of FLJ10374 may have cooperated to promote leukemogenesis in AML with t(9;11;19). © 2006 Wiley-Liss, Inc.

Experimental Cell Research, 2005

The small GTPase Rac1 can stimulate various signaling pathways following a tightly controlled GDP... more The small GTPase Rac1 can stimulate various signaling pathways following a tightly controlled GDP-GTP exchange. A splicing variant designated Rac1b was found to exist predominantly in the active GTP-bound state but the functional consequences of its expression remain unknown. Here we used mouse fibroblasts as a model to assess the signaling properties of Rac1b. We show that, in contrast to Rac1, expression of wild-type Rac1b is sufficient to stimulate cyclin D1 accumulation and G1/S progression in these cells. Moreover, expression of wild-type Rac1b, but not of wild-type Rac1, dramatically increased cell survival in the presence of only minimal growth stimuli. Both cellular responses were blocked by the NF-kappaB super-repressor IkappaBalpha(A32A36). Active Rac1b induced the phosphorylation and membrane translocation of IkappaBalpha, a prerequisite for the activation of NF-kappaB. These data demonstrate that Rac1b is a highly active Rac1 variant that stimulates cell cycle progression and cell survival in pathways involving NF-kappaB.

Pediatric Hematology and Oncology, 2001

p73, a recently identified gene showing high homology to p53 and mapping to 1p36.33, was presente... more p73, a recently identified gene showing high homology to p53 and mapping to 1p36.33, was presented as a candidate gene for neuroblastoma. In this study the authors evaluate the levels and allelic nature of p73 expression in primary neuroblastomas using reverse transcription-polymerase chain reaction-restriction fragment length polymorphism strategies based on intragenic polymorphisms. From 32 neuroblastoma patients, 11 were heterozygous for the p73 polymorphisms analyzed. p73 expression was found to be low in the correspondent tumors and while all 6 stages 1 and 2 tumors presented biallelic expression, 4 out of the 5 stage 4 tumors showed only one active p73 allele. Analysis of blood samples from 8 healthy donors and 4 neuroblastoma patients revealed much higher levels of p73 expression, and exclusively of biallelic nature. These results are supportive of a role for p73 in the biology of neuroblastoma, particularly in some advanced tumors. Nevertheless, the G81A/C91T polymorphism, previously implicated in regulating the expression of p73, did not show any significant association with neuroblastoma development.

Human Mutation, 2000

Hereditary non-polyposis colorectal cancer (HNPCC) is considered to be determined by germline mut... more Hereditary non-polyposis colorectal cancer (HNPCC) is considered to be determined by germline mutations in the mismatch repair (MMR) genes, especially MSH2 and MLH1. While screening for mutations in these two genes in HNPCC portuguese families, 3 previously unreported MSH2 and 1 MLH1 mutations have been identified in families meeting strict Amsterdam criteria.

Expert Review of Gastroenterology & Hepatology, 2009

Cellular Signalling, 2008

Keywords: ERK1/2 MAP kinase pathway MEK1 PAK1 Rac1 RhoA WNK protein kinases WNK2

Biochemical and Biophysical Research Communications, 2000

Here we present the complete structure of the human RAC1 gene and characterize its expression. Th... more Here we present the complete structure of the human RAC1 gene and characterize its expression. The gene comprises 7 exons over a length of 29 kb and is localized to chromosome 7p22. The GC-rich gene promoter shows characteristics of a housekeeping gene and Northern blot studies revealed ubiquitous expression of two rac1 transcripts, 1.2 and 2.5 kb in size. The two transcripts are expressed in tissuespecific ratios, reflecting competition between two alternative polyadenylation sites. The RAC1 but not RAC2 gene contains an additional exon 3b that is included by alternative splicing into the variant Rac1b, a constitutively active mutant which induces the formation of lamellipodia in fibroblasts. These data indicate that the RAC1 gene encodes two signaling GTPases. The gene structure reported here will enable studies on the regulation of RAC1 expression during tumorigenesis and development.

Gastroenterology, 2008

Background & Aims: In colorectal tumors, activating BRAF mutations occur alternative to KRAS onco... more Background & Aims: In colorectal tumors, activating BRAF mutations occur alternative to KRAS oncogenic mutations, but in cell culture possess a much lower transforming capacity. Rac1b, an hyperactive Rac1 spliced variant, is over-expressed in some colorectal tumors and activates the transcription factor NF-kB, which initiates a transcriptional response that promotes cell cycle progression and inhibits apoptose. The aim of this study was to determine whether Rac1b overexpression is associated with B-Raf V600E in primary colorectal tumors and whether a functional cooperation between these two proteins exists in colorectal cells with a wild-type KRAS genotype. Methods: Screening of BRAF and KRAS mutations by direct sequencing and Rac1b mRNA expression analysis by quantitative Real Time PCR were conducted in 74 samples (13 normal colonic mucosa, 45 primary colorectal tumors and, 16 colorectal cancer cell lines). RNA interference and focus formation assays were used to assess the cooperation between Rac1b and B-Raf V600E in cancer cell viability. Results: Rac1b overexpression and B-Raf V600E are significantly associated in primary colorectal tumors (P=0.008) and colorectal cell lines. The simultaneous suppression of both proteins dramatically decreased colorectal cancer cell viability through impaired cell cycle progression and increased apoptosis. Conclusions: Our data demonstrate that Rac1b and B-Raf V600E functionally cooperate to sustain colorectal cell viability and suggest they constitute an alternative survival pathway to oncogenic K-Ras. These results reveal a novel molecular characteristic of colon tumors containing B-Raf mutations and should help in defining novel targets for cancer therapy.

Human Molecular Genetics, 2009

The small GTPase Rac1 regulates signaling pathways controlling actin-dependent cell motility as w... more The small GTPase Rac1 regulates signaling pathways controlling actin-dependent cell motility as well as gene transcription. An alternative splicing variant Rac1b is overexpressed in a subset of colorectal tumors and is required to sustain tumor cell viability. Thus, it is of therapeutic interest to understand the molecular mechanism behind the overexpression of Rac1b through alternative splicing. Here we describe that ASF/SF2 and SRp20 are two antagonistic splicing factors regulating Rac1b expression in colorectal tumor cells. Using an Rac1 minigene, we identified that SRp20 increased skipping of alternative exon 3b in HT29 colorectal cells, whereas ASF/SF2 increased its inclusion. The depletion of the endogenous expression of these splicing factors by specific small interfering RNA confirmed that ASF/SF2 acts as an enhancer of endogenous Rac1b splicing, whereas SRp20 acts as a silencer. Point mutations in exon 3b defined two adjacent regulatory regions required for skipping or inclusion of exon 3b, which are recognized in vitro by SRp20 and ASF/ SF2, respectively. Both splicing factors were found to be regulated by upstream signaling pathways: the inhibition of the phosphatidylinositol 3-kinase pathway increased protein levels of ASF/SF2 and promoted Rac1b, whereas activation of b-catenin/TCF4 increased expression of SRp20 and inhibited that of Rac1b. Together, these data reveal that signaling pathways act in concert to target independent splicing factors and achieve the correct combinatorial code to regulate alternative splicing of the small GTPase Rac1.

Rna-a Publication of The Rna Society, 2008

Fisioterapia, 2006

Este estudio tiene como objetivo evaluar los indicadores antropométricos de las mujeres posmenopa... more Este estudio tiene como objetivo evaluar los indicadores antropométricos de las mujeres posmenopausias con edad de 45 hasta 65 años, con las diferencias fases de pérdida de la densidad ósea. La muestra fue constituida por 52 mujeres, las cuales fueron divididas en grupos de osteoporosis, formados por 23 mujeres (58,2 ± 3,3 años) y grupo de osteopenia formada por 29 mujeres (57,2 ± 6,1 años). La evaluación antropométrica obtuvo datos de la composición corporal, relación cintura-cadera (RCC), la suma de los pliegues del tronco y el índice de la masa corporal (IMC). Los procedimientos estadísticos fueron la media entre desvió-padrón y la amplitud de variación. El análisis del perfil de normalidad de las distribuciones, fue realizado por intermedio del test de Shapiro-Wilk, se utilizó el test T de medidas independientes y el test

Molecular Cancer Research, 2008

The small GTPase Rac1 can stimulate various signaling pathways that contribute to cell transforma... more The small GTPase Rac1 can stimulate various signaling pathways that contribute to cell transformation. In particular, the activation of the NFKB transcription factor initiates an antiapoptotic response and promotes cell cycle progression through increased cyclin D1 expression. As a potential oncogenic mechanism to up-regulate this pathway, the overexpression of the Rac1b splicing variant was reported in some colorectal tumors. Rac1b exists predominantly in the active GTP-bound state and selectively promotes the pathway leading to NFKB activation. Here, we studied the role of endogenous Rac1b in colorectal cancer cells. We found that depletion of Rac1b by small interfering RNAs inhibited endogenous NFKB activation and reduced cell viability to 50% within 48 hours. This reduction was due to increased apoptosis, although a reduced G 1 -S progression rate was also observed. These data show, for the first time, that colorectal cells expressing alternative spliced Rac1b also depend on Rac1b signaling to sustain their survival. (Mol Cancer Res

Biochemical and Biophysical Research Communications, 2000

Genes Chromosomes & Cancer, 2006

The MLL gene, at 11q23, undergoes chromosomal translocation with a large number of partner genes ... more The MLL gene, at 11q23, undergoes chromosomal translocation with a large number of partner genes in both acute lymphoblastic and acute myeloid leukemia (AML). We report a novel t(9;11;19)(p22;q23;p13.3) disrupting MLL in an infant AML patient. The 5′ end of MLL fused to chromosome 9 sequences on the der(11), whereas the 3′ end was translocated to chromosome 19. We developed long-distance inverse–polymerase chain reaction assays to investigate the localization of the breakpoints on der(11) and der(19). We found that intron 5 of MLL was fused to intron 5 of MLLT3 at the der(11) genomic breakpoint, resulting in a novel in-frame MLL exon 5–MLLT3 exon 6 fusion transcript. On the der(19), a novel gene annotated as FLJ10374 was disrupted by the breakpoint. Using reverse transcription–polymerase chain reaction analysis, we showed that FLJ10374 is ubiquitously expressed in human cells. Transfection of the FLJ10374 protein in different cell lines revealed that it localized exclusively to the nucleus. In serum-starved NIH-3T3 cells, the expression of FLJ10374 decreased the rate of the G1-to-S transition of the cell cycle, whereas the suppression of FLJ10374 through short interfering RNA increased cell proliferation. These results indicate that FLJ10374 negatively regulates cell cycle progression and proliferation. Thus, a single chromosomal rearrangement resulting in formation of the MLL–MLLT3 fusion gene and haplo-insufficiency of FLJ10374 may have cooperated to promote leukemogenesis in AML with t(9;11;19). © 2006 Wiley-Liss, Inc.

Experimental Cell Research, 2005

The small GTPase Rac1 can stimulate various signaling pathways following a tightly controlled GDP... more The small GTPase Rac1 can stimulate various signaling pathways following a tightly controlled GDP-GTP exchange. A splicing variant designated Rac1b was found to exist predominantly in the active GTP-bound state but the functional consequences of its expression remain unknown. Here we used mouse fibroblasts as a model to assess the signaling properties of Rac1b. We show that, in contrast to Rac1, expression of wild-type Rac1b is sufficient to stimulate cyclin D1 accumulation and G1/S progression in these cells. Moreover, expression of wild-type Rac1b, but not of wild-type Rac1, dramatically increased cell survival in the presence of only minimal growth stimuli. Both cellular responses were blocked by the NF-kappaB super-repressor IkappaBalpha(A32A36). Active Rac1b induced the phosphorylation and membrane translocation of IkappaBalpha, a prerequisite for the activation of NF-kappaB. These data demonstrate that Rac1b is a highly active Rac1 variant that stimulates cell cycle progression and cell survival in pathways involving NF-kappaB.

Pediatric Hematology and Oncology, 2001

p73, a recently identified gene showing high homology to p53 and mapping to 1p36.33, was presente... more p73, a recently identified gene showing high homology to p53 and mapping to 1p36.33, was presented as a candidate gene for neuroblastoma. In this study the authors evaluate the levels and allelic nature of p73 expression in primary neuroblastomas using reverse transcription-polymerase chain reaction-restriction fragment length polymorphism strategies based on intragenic polymorphisms. From 32 neuroblastoma patients, 11 were heterozygous for the p73 polymorphisms analyzed. p73 expression was found to be low in the correspondent tumors and while all 6 stages 1 and 2 tumors presented biallelic expression, 4 out of the 5 stage 4 tumors showed only one active p73 allele. Analysis of blood samples from 8 healthy donors and 4 neuroblastoma patients revealed much higher levels of p73 expression, and exclusively of biallelic nature. These results are supportive of a role for p73 in the biology of neuroblastoma, particularly in some advanced tumors. Nevertheless, the G81A/C91T polymorphism, previously implicated in regulating the expression of p73, did not show any significant association with neuroblastoma development.

Human Mutation, 2000

Hereditary non-polyposis colorectal cancer (HNPCC) is considered to be determined by germline mut... more Hereditary non-polyposis colorectal cancer (HNPCC) is considered to be determined by germline mutations in the mismatch repair (MMR) genes, especially MSH2 and MLH1. While screening for mutations in these two genes in HNPCC portuguese families, 3 previously unreported MSH2 and 1 MLH1 mutations have been identified in families meeting strict Amsterdam criteria.

Expert Review of Gastroenterology & Hepatology, 2009

Cellular Signalling, 2008

Keywords: ERK1/2 MAP kinase pathway MEK1 PAK1 Rac1 RhoA WNK protein kinases WNK2

Biochemical and Biophysical Research Communications, 2000

Here we present the complete structure of the human RAC1 gene and characterize its expression. Th... more Here we present the complete structure of the human RAC1 gene and characterize its expression. The gene comprises 7 exons over a length of 29 kb and is localized to chromosome 7p22. The GC-rich gene promoter shows characteristics of a housekeeping gene and Northern blot studies revealed ubiquitous expression of two rac1 transcripts, 1.2 and 2.5 kb in size. The two transcripts are expressed in tissuespecific ratios, reflecting competition between two alternative polyadenylation sites. The RAC1 but not RAC2 gene contains an additional exon 3b that is included by alternative splicing into the variant Rac1b, a constitutively active mutant which induces the formation of lamellipodia in fibroblasts. These data indicate that the RAC1 gene encodes two signaling GTPases. The gene structure reported here will enable studies on the regulation of RAC1 expression during tumorigenesis and development.

Gastroenterology, 2008

Background & Aims: In colorectal tumors, activating BRAF mutations occur alternative to KRAS onco... more Background & Aims: In colorectal tumors, activating BRAF mutations occur alternative to KRAS oncogenic mutations, but in cell culture possess a much lower transforming capacity. Rac1b, an hyperactive Rac1 spliced variant, is over-expressed in some colorectal tumors and activates the transcription factor NF-kB, which initiates a transcriptional response that promotes cell cycle progression and inhibits apoptose. The aim of this study was to determine whether Rac1b overexpression is associated with B-Raf V600E in primary colorectal tumors and whether a functional cooperation between these two proteins exists in colorectal cells with a wild-type KRAS genotype. Methods: Screening of BRAF and KRAS mutations by direct sequencing and Rac1b mRNA expression analysis by quantitative Real Time PCR were conducted in 74 samples (13 normal colonic mucosa, 45 primary colorectal tumors and, 16 colorectal cancer cell lines). RNA interference and focus formation assays were used to assess the cooperation between Rac1b and B-Raf V600E in cancer cell viability. Results: Rac1b overexpression and B-Raf V600E are significantly associated in primary colorectal tumors (P=0.008) and colorectal cell lines. The simultaneous suppression of both proteins dramatically decreased colorectal cancer cell viability through impaired cell cycle progression and increased apoptosis. Conclusions: Our data demonstrate that Rac1b and B-Raf V600E functionally cooperate to sustain colorectal cell viability and suggest they constitute an alternative survival pathway to oncogenic K-Ras. These results reveal a novel molecular characteristic of colon tumors containing B-Raf mutations and should help in defining novel targets for cancer therapy.

Human Molecular Genetics, 2009

The small GTPase Rac1 regulates signaling pathways controlling actin-dependent cell motility as w... more The small GTPase Rac1 regulates signaling pathways controlling actin-dependent cell motility as well as gene transcription. An alternative splicing variant Rac1b is overexpressed in a subset of colorectal tumors and is required to sustain tumor cell viability. Thus, it is of therapeutic interest to understand the molecular mechanism behind the overexpression of Rac1b through alternative splicing. Here we describe that ASF/SF2 and SRp20 are two antagonistic splicing factors regulating Rac1b expression in colorectal tumor cells. Using an Rac1 minigene, we identified that SRp20 increased skipping of alternative exon 3b in HT29 colorectal cells, whereas ASF/SF2 increased its inclusion. The depletion of the endogenous expression of these splicing factors by specific small interfering RNA confirmed that ASF/SF2 acts as an enhancer of endogenous Rac1b splicing, whereas SRp20 acts as a silencer. Point mutations in exon 3b defined two adjacent regulatory regions required for skipping or inclusion of exon 3b, which are recognized in vitro by SRp20 and ASF/ SF2, respectively. Both splicing factors were found to be regulated by upstream signaling pathways: the inhibition of the phosphatidylinositol 3-kinase pathway increased protein levels of ASF/SF2 and promoted Rac1b, whereas activation of b-catenin/TCF4 increased expression of SRp20 and inhibited that of Rac1b. Together, these data reveal that signaling pathways act in concert to target independent splicing factors and achieve the correct combinatorial code to regulate alternative splicing of the small GTPase Rac1.

Rna-a Publication of The Rna Society, 2008