Benoît Grondin - Academia.edu (original) (raw)

Papers by Benoît Grondin

Journal of Biological Chemistry, Aug 1, 1991

Blood, Nov 16, 2004

The gene coding for the pro-inflammatory cytokine IL-1β is induced at the transcription level in ... more The gene coding for the pro-inflammatory cytokine IL-1β is induced at the transcription level in differentiating macrophages and in stress response. Interestingly, PU.1 and C/EBPβ, two transcription factors implicated in IL-1β gene expression are not induced by stress exposure, while c-Jun is strongly induced. Strikingly, this upregulation of c-Jun is required for IL-1β induction, as cells expressing a c-Jun antisense construct fail to respond to stress exposure. We have mapped the induction of IL-1β gene expression to its proximal promoter and show that it is mediated by the transcriptional synergy between C/EBPβ, c-Jun and PU.1 via specific DNA binding sites for C/EBPβ and PU.1 only. To elucidate how PU.1 and C/EBPβ cooperate with c-Jun at the molecular level, we have optimized a DNA binding assay based on IL-1β promoter fragments immobilized on beads to isolate protein complexes from nuclear extracts, which were subsequently eluted and identified by Western blotting. We show that PU.1 or C/EBPβ alone directly bind this promoter fragment via specific sequences while purified recombinant c-Jun fails to do so. However, the presence of either PU.1 or C/EBPβ on the promoter allows for a recruitment of c-Jun to the DNA template, mediated by direct protein-protein interaction. Interestingly, the leucine zipper domain of c-Jun is essential for its interaction with C/EBPβ while dispensable for PU.1 interaction in vitro whereas its basic domain is required for both interactions. Furthermore, we show that PU.1 and C/EBPβ cooperatively bind the IL-1β promoter, resulting in a synergistic recruitment of c-Jun. Finally, we show that the strength of interaction of c-Jun mutants with PU.1 or C/EBPβ determine the strength of transcription output and c-Jun mutants that fail to associate with either PU.1 or C/EBPβ are transcriptionally inactive. In contrast, c-Jun mutants exhibiting increased homodimerization are more active that the wild type protein. Taken together, our data suggest that c-Jun homodimers can be targeted to the IL-1β promoter in the absence of a specific DNA binding element, and conclude that PU.1 and C/EBPβ are specifically tethered to the IL-1β promoter while c-Jun cooperatively binds these proteins and acts as a transcriptional co-activator. We propose a mechanism based on an initial binding of PU.1 and C/EBPβ to the IL-1β promoter followed by a cooperative recruitment of c-Jun, resulting in transcriptional synergy and IL-1β gene expression in stress response.

Life science alliance, May 23, 2023

CHARGE syndrome is a neural crest-related disorder mainly caused by mutation of the chromatin rem... more CHARGE syndrome is a neural crest-related disorder mainly caused by mutation of the chromatin remodeler-coding gene CHD7. Alternative causes include mutation of other chromatin and/or splicing factors. One of these additional players is the poorly characterized FAM172A, which we previously found in a complex with CHD7 and the small RNA-binding protein AGO2 at the chromatin-spliceosome interface. Focusing on the FAM172A-AGO2 interplay, we now report that FAM172A is a direct binding partner of AGO2 and, as such, one of the long sought-after regulators of AGO2 nuclear import. We show that this FAM172A function mainly relies on its classical bipartite nuclear localization signal and associated canonical importin-α/β pathway, being enhanced by CK2-induced phosphorylation and abrogated by a CHARGE syndrome-associated missense mutation. Overall, this study thus strengthens the notion that noncanonical nuclear functions of AGO2 and associated regulatory mechanisms might be clinically relevant.

Blood, Nov 16, 2007

In acute promyelocytic leukemia (APL), the variant t(15;17) translocation is responsive to differ... more In acute promyelocytic leukemia (APL), the variant t(15;17) translocation is responsive to differentiation therapy with retinoic acid (RA) while the t(11;17) APL is a more aggressive disease with poor prognosis. The latter produces two fusion proteins, PLZF-RARa and RARa-PLZF, and both proteins are required for leukemogenesis. To define the role of RARa-PLZF, we ectopically expressed the fusion gene in 32D cells and in primary bone marrow cells. First, our results show that RARa-PLZF inhibits myeloid gene expression, specifically CEBPa targets, which fulfill important function in cell survival and differentiation along the granulocytic lineage. Second, we found that repression by RARa-PLZF is dependent on the binding of C/EBPa to its cognate sequence in the promoter of CEBPa target gene, GCSFR. Third, we confirmed by chromatin immuprecipitation that RARa-PLZF associate with C/EBPa on DNA. Fourth, we showed that as PLZF, RARa-PLZF interact directly with HDAC1 and that this interaction causes a deacetylation of histone H3 at the promoter. This inhibition is reversed by treatment with histone deacetylase inhibitor (TSA) both in vitro and in vivo. Thus, this repression is dependent on direct interaction of RP with C/EBPa and recruitment of HDAC1, causing histone deacetylation at C/EBPa target loci. Finally, our data indicate that C/EBPa activity is severely impaired in leukemic cells from patients with t(11;17) APL, as compared to the t(15;17) APL, which is more amenable to therapy. In summary, our study indicates that the oncogene RARa-PLZF inhibits C/EBPa function through direct protein-protein interaction, and thus contributes to leukemogenesis in t(11;17) APL.

Metabolic reprogramming is a hallmark of cancer that includes increased glucose uptake and accele... more Metabolic reprogramming is a hallmark of cancer that includes increased glucose uptake and accelerated aerobic glycolysis. This phenotype is required to fulfill anabolic demands associated with aberrant cell proliferation and is often mediated by oncogenic drivers such as activated BRAF. In this study, we show that the MAPK-activated p90 ribosomal S6 kinase (RSK) is necessary to maintain glycolytic metabolism in BRAF-mutated melanoma cells. RSK directly phosphorylated the regulatory domain of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 2 (PFKFB2), an enzyme that catalyzes the synthesis of fructose-2,6-bisphosphate during glycolysis. Inhibition of RSK reduced PFKFB2 activity and glycolytic flux in melanoma cells, suggesting an important role for RSK in BRAF-mediated metabolic rewiring. Consistent with this, expression of a phosphorylation-deficient mutant of PFKFB2 decreased aerobic glycolysis and reduced the growth of melanoma in mice. Together, these results indicate that RSK-mediated phosphorylation of PFKFB2 plays a key role in the metabolism and growth of BRAF-mutated melanomas.Significance: RSK promotes glycolytic metabolism and the growth of BRAF-mutated melanoma by driving phosphorylation of an important glycolytic enzyme. Cancer Res; 78(9); 2191–204. ©2018 AACR.

Nature Communications

Melanoma is the deadliest form of skin cancer and considered intrinsically resistant to chemother... more Melanoma is the deadliest form of skin cancer and considered intrinsically resistant to chemotherapy. Nearly all melanomas harbor mutations that activate the RAS/mitogen-activated protein kinase (MAPK) pathway, which contributes to drug resistance via poorly described mechanisms. Herein we show that the RAS/MAPK pathway regulates the activity of cyclin-dependent kinase 12 (CDK12), which is a transcriptional CDK required for genomic stability. We find that melanoma cells harbor constitutively high CDK12 activity, and that its inhibition decreases the expression of long genes containing multiple exons, including many genes involved in DNA repair. Conversely, our results show that CDK12 inhibition promotes the expression of short genes with few exons, including many growth-promoting genes regulated by the AP-1 and NF-κB transcription factors. Inhibition of these pathways strongly synergize with CDK12 inhibitors to suppress melanoma growth, suggesting promising drug combinations for mor...

Cell Reports, 2020

Highlights d Depletion of NF45 or NF90 leads to pleiotropic mitotic defects d The NF45-NF90 compl... more Highlights d Depletion of NF45 or NF90 leads to pleiotropic mitotic defects d The NF45-NF90 complex associates with, and regulates, a cluster of mitotic mRNAs d The proximity interactome of NF45 and NF90 reveals Stau1 and Stau2 d Depletion of Stau1/2 rescues mitotic defects induced by loss of NF45 or NF90

Blood, 2005

Members of the paired class of homeobox proteins are critical determinants of left-right asymmetr... more Members of the paired class of homeobox proteins are critical determinants of left-right asymmetry and establish the antero-posterior axis, suggesting that they could also be involved in asymmetric determination within the hematopoietic system. We have previously shown that mice lacking Otx1, a bicoid homeodomain-containing gene, exhibit an impairment of the erythroid compartment, associated with decreased SCL levels. In the present study, we show that Otx1 is coexpressed with SCL in yolk sac during embryonic development; in differentiating embryonic stem cells, Otx1 is upregulated with SCL in both primitive and definitive erythroid colonies, while Otx expression is absent in cardiomyocytes and skeletomyocytes. To address the role of Otx1 in hematopoiesis, we overexpressed Otx1 in primary hematopoietic cells using the MSCV retrovirus. The gain of Otx1 function gives rise to a 6-fold increase in endogenous SCL levels together with an increase in TER119-positive erythroid cells. Strik...

Blood, 2015

Oncogenic transcription factors are major drivers in acute leukemias. These oncogenes are believe... more Oncogenic transcription factors are major drivers in acute leukemias. These oncogenes are believed to subvert normal cell identity via the establishment of gene expression programs that dictate cell differentiation and growth. The LMO2 oncogene, which is commonly activated in T-cell acute lymphoblastic leukemia (T-ALL), has a well-established function in transcription regulation. We and others previously demonstrated that LMO1 or LMO2 collaborate with the SCL transcription factor to activate a self-renewal program that converts non self-renewing progenitors into pre-leukemic stem cells. Here we demonstrate a non-transcriptional role of LMO2 in controlling cell fate by directly promoting DNA replication, a hitherto unrecognized mechanism that might also account for its oncogenic properties. To address the question whether LMO2 controls other functions via protein-protein interactions, we performed a proteome-wide screen for LMO2 interaction partners in Kit+ Lin- cells. In addition to...

Cancer research, Jan 12, 2018

Biochemical Journal, 1993

Processing of N-linked oligosaccharides in Saccharomyces cerevisiae begins with the removal of gl... more Processing of N-linked oligosaccharides in Saccharomyces cerevisiae begins with the removal of glucose and mannose residues from Glc3Man9GlcNAc2 to form a single isomer of Man8GlcNAc2. The importance of mannose removal for subsequent outer chain synthesis was examined in strains of S. cerevisiae disrupted in the MNS1 gene encoding a specific alpha 1,2-mannosidase responsible for Man8GlcNAc2 synthesis [Camirand, Heysen, Grondin and Herscovics (1991) J. Biol. Chem. 266, 15120-15127]. Both MNS1 transcripts of 1.85 kb and 1.7 kb were not observed in Northern blots of mns1 cells (i.e. cells containing the disrupted gene). Analysis on Bio-Gel P-6 of endo-beta-N-acetylglucosaminidase-H-sensitive oligosaccharides following a 10 min pulse with [2-3H]mannose revealed similar amounts of labelled outer chains excluded from the gel in both control and mns1 cells. H.p.l.c. of the included oligosaccharides showed that a Man9GlcNAc, rather than a Man8GlcNAc, intermediate was formed in mns1 cells. A...

bioRxiv (Cold Spring Harbor Laboratory), Mar 5, 2022

The poorly characterized protein FAM172A is mutated in some individuals affected by a disorder of... more The poorly characterized protein FAM172A is mutated in some individuals affected by a disorder of neural crest development called CHARGE syndrome. We also know that FAM172A can interact with the main CHARGE syndrome-associated protein CHD7 and the small RNA-binding protein AGO2 at the chromatin-spliceosome interface. Focusing on this intriguing FAM172A-AGO2 interaction, we now report that FAM172A is one of the long sought-after regulator of AGO2 nuclear import. This FAM172A function relies on its nuclear localization signal, being enhanced by CK2-mediated phosphorylation and abrogated by a CHARGE syndromeassociated missense mutation. Accordingly, Fam172a and Ago2 genetically interact in mice, and neural crest-specific depletion of Ago2 is sufficient to phenocopy CHARGE syndrome without impacting post-transcriptional gene silencing. Rapamycin-mediated rescue suggests that observed morphological anomalies are instead due to alternative splicing defects. This work thus demonstrates that non-canonical nuclear functions of AGO2 and associated regulatory mechanisms may be clinically relevant. .

Journal of Biological Chemistry, 1989

We have isolated the gene from Saccharomyces cerevisiae encoding an alpha-mannosidase of unique s... more We have isolated the gene from Saccharomyces cerevisiae encoding an alpha-mannosidase of unique specificity which catalyzes the removal of one mannose residue from Man9GlcNAc to produce a single isomer of Man8GlcNAc (Jelinek-Kelly, S., and Herscovics, A. (1988) J. Biol. Chem. 263, 14757-14763). Amino acid sequence information was obtained and corresponding degenerate oligonucleotide primers were synthesized for polymerase chain reactions on yeast genomic DNA. The labeled polymerase chain reaction products were used to screen a S. cerevisiae genomic library in YEp24, and positive clones of different lengths with similar restriction maps were isolated. A 4.6-kilobase fragment which hybridized with the probes was sequenced. It contained a 1650-base pair open reading frame encoding peptide sequences corresponding to the amino acid sequences of the purified alpha-mannosidase. The gene, designated MNS1, encodes a 549-amino acid polypeptide of calculated molecular size 63,017 Da produced by an mRNA species of approximately 1.7 kilobases. The protein possesses a putative noncleavable signal sequence near its N-terminal region which probably acts as a transmembrane domain. It has three potential N-glycosylation sites and a calcium-binding consensus sequence. Its amino acid sequence is homologous to the recently isolated cDNA from rabbit liver alpha-1,2 mannosidase which can transform Man9GlcNAc to Man5GlcNAc (Moremen, K. W., Schutzbach, J. S., Forsee, W. T., Neame, P., Bishoff, J., Lodish, H. F., and Robbins, P. W. (1990) Glycoconjugate J. 7, 401). Overexpression of the MNS1 gene caused an 8-10-fold increase in specific alpha-mannosidase activity. Disruption of the MNS1 gene resulted in undetectable specific alpha-mannosidase activity but no apparent effect on growth. These results demonstrate that MNS1 is the structural gene for the specific alpha-mannosidase and that its activity is not essential for viability.

Proceedings of the National Academy of Sciences of the United States of America, Jan 13, 2016

Oncogenic transcription factors are commonly activated in acute leukemias and subvert normal gene... more Oncogenic transcription factors are commonly activated in acute leukemias and subvert normal gene expression networks to reprogram hematopoietic progenitors into preleukemic stem cells, as exemplified by LIM-only 2 (LMO2) in T-cell acute lymphoblastic leukemia (T-ALL). Whether or not these oncoproteins interfere with other DNA-dependent processes is largely unexplored. Here, we show that LMO2 is recruited to DNA replication origins by interaction with three essential replication enzymes: DNA polymerase delta (POLD1), DNA primase (PRIM1), and minichromosome 6 (MCM6). Furthermore, tethering LMO2 to synthetic DNA sequences is sufficient to transform these sequences into origins of replication. We next addressed the importance of LMO2 in erythroid and thymocyte development, two lineages in which cell cycle and differentiation are tightly coordinated. Lowering LMO2 levels in erythroid progenitors delays G1-S progression and arrests erythropoietin-dependent cell growth while favoring term...

The specific $ alpha$-mannosidase of the yeast Saccharomyces cerevisiae involved in the early pro... more The specific $ alpha$-mannosidase of the yeast Saccharomyces cerevisiae involved in the early processing of N-linked oligosaccharides converts Man$ sb9$GlcNAc$ sb2$ to Man$ sb8$GlcNAc$ sb2$ prior to elongation of the sugar chains with mannose residues. This membrane enzyme is believed to be associated with elements of the endoplasmic reticulum. The membrane topology of the yeast $ alpha$-mannosidase was determined by cell-free transcription and translation in a reticulocyte lysate in the presence of dog pancreas microsomes. It was demonstrated that the $ alpha$-mannosidase has a type II membrane topology in vesicles similar to that of all the Golgi glycosyltransferases and glycosidases cloned to date. The enzyme was expressed as a fusion protein in E. coli to produce antisera that will be used to immunolocalize the enzyme in yeast cells. The yeast $ alpha$-mannosidase gene lacking the NH2-terminal hydrophobic signal/anchor sequence was fused to the COOH-terminus of the Schistosoma j...

Experimental Hematology, 2014

Proceedings of the National Academy of Sciences, 2013

In acute promyelocytic leukemia, granulocytic differentiation is arrested at the promyelocyte sta... more In acute promyelocytic leukemia, granulocytic differentiation is arrested at the promyelocyte stage. The variant t(11;17) translocation produces two fusion proteins, promyelocytic leukemia zinc finger-retinoic acid receptor α (PLZF-RARα) and RARα-PLZF, both of which participate in leukemia development. Here we provide evidence that the activity of CCAAT/enhancer binding protein α (C/EBPα), a master regulator of granulocytic differentiation, is severely impaired in leukemic promyelocytes with the t(11;17) translocation compared with those associated with the t(15;17) translocation. We show that RARα-PLZF inhibits myeloid cell differentiation through interactions with C/EBPα tethered to DNA, using ChIP and DNA capture assays. Furthermore, RARα-PLZF recruits HDAC1 and causes histone H3 deacetylation at C/EBPα target loci, thereby decreasing the expression of C/EBPα target genes. In line with these results, HDAC inhibitors restore in part C/EBPα target gene expression. These findings pr...

Journal of Virology, 2000

Infected-cell polypeptide 4 (ICP4) of herpes simplex virus type 1 (HSV-1) activates the expressio... more Infected-cell polypeptide 4 (ICP4) of herpes simplex virus type 1 (HSV-1) activates the expression of many HSV genes during infection. It functions along with the cellular general transcription factors to increase the transcription rates of genes. In this study, an HSV late promoter consisting of only a TATA box and an INR element was immobilized on a magnetic resin and incubated with nuclear extracts or purified TFIID in the presence and absence of ICP4. Analysis of the complexes formed on these promoters revealed that ICP4 increased the formation of transcription preinitiation complexes (PICs) in a TATA box-dependent manner, as determined by the presence of ICP4, TFIID, TFIIB, and polymerase II on the promoter. With both nuclear extract and purified TFIID, it was determined that ICP4 helped TFIID bind to the promoter and the TATA box. These observations differed from those for the activator Gal4-VP16. As previously observed by others, Gal4-VP16 also increased the formation of PICs...