Tapas Saha - Academia.edu (original) (raw)

Papers by Tapas Saha

Environment and Ecology, 2009

Nar, 2003

We show here that under physiologically reasonable conditions, CGG repeats in RNA readily form ha... more We show here that under physiologically reasonable conditions, CGG repeats in RNA readily form hairpins. In contrast to its DNA counterpart that forms a complex mixture of hairpins and tetraplexes, r(CGG) 22 forms a single stable hairpin with no evidence for any other folded structure even at low pH. RNA with the sequence (CGG) 9 AGG (CGG) 12 AGG(CGG) 97 , found in a fragile X syndrome pre-mutation allele, forms a number of different hairpins. The most prominent hairpin forms in the 3¢ part of the repeat and involves the 97 uninterrupted CGG repeats. In contrast to the CUG-RNA hairpins formed by myotonic dystrophy type 1 repeats, we found no evidence that CGG-RNA hairpins activate PKR, the interferon-inducible protein kinase that is activated by a wide range of double-stranded RNAs. However, we do show that the CGG-RNA is digested, albeit inef®ciently, by the human Dicer enzyme, a step central to the RNA interference effect on gene expression. These data provide clues to the basis of the toxic effect of CGG-RNA that is thought to occur in fragile X pre-mutation carriers. In addition, RNA hairpins may also account for the stalling of the 40S ribosomal subunit that is thought to contribute to the translation de®cit in fragile X pre-mutation and full mutation alleles.

Indian Journal of Chemistry Sect B Organic Chemistry Including Medical Chemistry, 1998

Polymer Plastics Technology and Engineering, Sep 22, 2006

A number of formulations were developed using urethane diacry-late oligomer in combination with a... more A number of formulations were developed using urethane diacry-late oligomer in combination with a series of monofunctional and multifunctional reactive diluents possessing diverse glass transi-tion temperatures from -50°C to 250°C. Films prepared with these formulations ...

Toxicological Environmental Chemistry, 1997

Different biotic and abiotic factors were found to play a vital role in attenuating metalaxyl res... more Different biotic and abiotic factors were found to play a vital role in attenuating metalaxyl residues in soil. In addition to metalaxyl many other products were found by HPLC and GC‐MS analysis while studying its soil metabolism in presence of natural sunlight. Three compounds were identified and characterized: 2,6‐dimethylaniline, 2,6‐dimethyl‐N‐ethylacetanilide and N‐(2,6‐dimethyl phenyl) alanine methyl ester.

Proceedings of 1994 4th International Conference on Properties and Applications of Dielectric Materials (ICPADM), 2000

... The bulk insulation in a transformer consists of cellulosic material (paper. presslloard and ... more ... The bulk insulation in a transformer consists of cellulosic material (paper. presslloard and transformerboard) and mineral oil. The cellulosic nia-terials and oil insulation used in transfornier degrade with time. ... (41 R. Evans. R. 8. Wearne and AF A. Wallis. Jnl. of .4pp. ...

Bjog an International Journal of Obstetrics Gynaecology, 2005

Objectives To compare transvaginal ultrasound measurements of endometrial thickness with direct a... more Objectives To compare transvaginal ultrasound measurements of endometrial thickness with direct anatomical measurements and consider the implications of these findings on clinical practice. Design Prospective observational study using two modalities blinded to each other's findings.

Oxidative medicine and cellular longevity

ABSTRACT

150 RING FINGER-DEPENDENT UBIQUITINATION BY PRAJA IS DEPENDENT ON TGF-BETA AND POTENTIALLY DEFINE... more 150 RING FINGER-DEPENDENT UBIQUITINATION BY PRAJA IS DEPENDENT ON TGF-BETA AND POTENTIALLY DEFINES THE FUNCTIONAL STATUS OF THE TUMOR SUPPRESSOR ELF IN HEPATOCELLULAR CANCER. Lopa Mishra, Tapas Saha, Bibhuti Mishra, Eugene Volpe, Yi Tang, Varalakshmi Katuri, Wilma Jogunoori, Deena Vardhini, Georgetown University, Washington, DC; Dale Haines, Temple University, Philadelphia, PA; Xuan Zhou, Ian Gallicano, Richard Schlegel. Georgetown University, Washington, DC. The TGF-b superfamily plays diverse and essential roles in cell differentiation and liver development, as well as in both suppression and formation of hepatocellular carcinoma (HCC). Precise modulation of TGF-b is through Smad activation by the type I receptors, and is dependent upon adaptor proteins such as ELF, a b-spectrin as well as modifying E-3 ligases such as SMURFs and PRAJA. Interestingly nearly two thirds of elf+/- mutant mice develop hepatocellular carcinoma spontaneously at 12-15 months. PRAJA is expressed in abunda...

T1667 Novel Therapeutic Targets for Gastrointestinal Cancer Eugene A. Volpe, Tapas Saha, Will J. ... more T1667 Novel Therapeutic Targets for Gastrointestinal Cancer Eugene A. Volpe, Tapas Saha, Will J. Ferguson, Yi Tang, Varalakshmi Katuri, Wilma Jogunoori, Tiffany M. Blake, Bubhuti Mishra, Lopa Mishra, Stephen R.T. Evans The TGF-β superfamily plays an important role in the formation of gastrointestinal carcinoma, cell differentiation, tumor suppression and liver development. The TGF-β pathway is inactivated in most gastrointestinal cancers. TGF-β is modulated through Smad activation and is dependent upon adaptor proteins such as ELF, a β-spectrin as well as modifying E3 ligases such as PRAJA. We have shown that disruption of the Smad4 adaptor protein ELF, a β-spectrin, disrupts TGF-β signaling. Elf-/- mice die in midgestation from gastrointestinal, liver, neural and heart defects. Aim: To identify new therapeutic targets to control gastrointestinal cancer when the TGF-β signaling pathway is inactivated. Methods and Results: 1. We performed protein kinase assays and microarray analysis...

T1624 TGF-β Modulates Ubiquitination of Tumor Suppressor, ELF, and SMAD3, by Praja, An E3 Ligase,... more T1624 TGF-β Modulates Ubiquitination of Tumor Suppressor, ELF, and SMAD3, by Praja, An E3 Ligase, That Control Hepatocellular Cancer Tapas Saha, Varalakshmi Katuri, Hye Baek, Sang S. Kim, Yi Tang, Wilma Jogunoori, Eugene A. Volpe, Bibhuti Mishra, Lopa Mishra The TGF-β superfamily plays essential roles in cell differentiation and liver development, as well as in both suppression and formation of hepatocellular carcinoma (HCC). TGF-β is modulated through Smad activation and is dependent upon adaptor proteins such as ELF, a â-spectrin as well as modifying E3 ligases such as PRAJA. Interestingly nearly two thirds of elf+/- mutant mice develop hepatocellular carcinoma spontaneously at 12-15 months. PRAJA is expressed in abundance in HCC and is an E3 ligase regulated by TGF-β and BMPs. Aims: To analyze molecular interactions between ELF, Smad3 and PRAJA in TGF-β/BMP signaling pathway in both normal liver formation and in HCC. Methods and Results: 1. PRAJA is expressed in hepatocyte progen...

1098 IDENTIFICATION OF MOLECULAR TARGETS FOR HEPATOCELLULAR CANCER AND ELF PHOSPHORYLATION BY TGF... more 1098 IDENTIFICATION OF MOLECULAR TARGETS FOR HEPATOCELLULAR CANCER AND ELF PHOSPHORYLATION BY TGF-BETA RECEPTOR I IN HEPATOCELLULAR CARCINOMA. Eugene A. Volpe1, Tapas Saha1, Yi Tang1, Bibhuti Mishra1, Lopa Mishra1,2, Lynt B. Johnson1, Stephen RT Evans1; 1Departments of Surgical Sciences, Medicine, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC; 2Department of Veterans Affairs Medical Center, Washington, DC. BACKGROUND: Transforming growth factor beta (TGF-b) signaling through Smad proteins is involved in regulation of cell growth, differentiation and lineage in a wide variety of tissues (Mishra et al., 2005). Smad modulation is dependent upon adaptor proteins and E3 ligases. Differential expression of PRAJA and ELF (embryonic liver fodrin) in hepatocellular cancer cells (HCC) and disruption of ELF, a Smad4 adaptor protein, inactivates TGF-b signaling in elf+/- mutant mice that develop hepatocellular cancers (Tang et al., 2003). PRAJA is a novel RING fing...

153 TGF-β PATHWAY MEMBERS SMAD3 AND ELF ARE KEY REGULATORS OF HEPATOCELLULAR CANCERS Young Woo Ki... more 153 TGF-β PATHWAY MEMBERS SMAD3 AND ELF ARE KEY REGULATORS OF HEPATOCELLULAR CANCERS Young Woo Kim1, Peter Kreishman2, Chohee Yun1, Wilma Jogunoori1, Eugene A. Volpe1, Tapas Saha1, Jonathan S. Mendelson1, Tiffany M. Blake1, Michael J. Pishvaian1, Yi Tang1, Bibhuti Mishra1, Lopa Mishra1,2; 1Surgery, Georgetown University, Washington, DC; 2DVAMC, Washington, DC The transforming growth factor-β (TGF-β) pathway constitutes a central signaling network that plays an essential role in cell differentiation, proliferation, motility, apoptosis and tumorigenesis. TGF-β signals are conveyed through type I/II receptors to specific intracellular mediators known as SMAD. Activation of SMAD3, a receptor activated SMAD, results in nuclear translocation and activation of target genes. We have shown that the adaptor protein ELF plays a key role in TGF-β signaling through SMAD3 and SMAD4 (Science, 2003, 299:574-577). Further analysis has revealed that over 40% of elf+/- mice spontaneously develop hepat...

2013 IEEE International Conference on Industrial Technology (ICIT), 2013

Environment and Ecology, 2009

Nar, 2003

We show here that under physiologically reasonable conditions, CGG repeats in RNA readily form ha... more We show here that under physiologically reasonable conditions, CGG repeats in RNA readily form hairpins. In contrast to its DNA counterpart that forms a complex mixture of hairpins and tetraplexes, r(CGG) 22 forms a single stable hairpin with no evidence for any other folded structure even at low pH. RNA with the sequence (CGG) 9 AGG (CGG) 12 AGG(CGG) 97 , found in a fragile X syndrome pre-mutation allele, forms a number of different hairpins. The most prominent hairpin forms in the 3¢ part of the repeat and involves the 97 uninterrupted CGG repeats. In contrast to the CUG-RNA hairpins formed by myotonic dystrophy type 1 repeats, we found no evidence that CGG-RNA hairpins activate PKR, the interferon-inducible protein kinase that is activated by a wide range of double-stranded RNAs. However, we do show that the CGG-RNA is digested, albeit inef®ciently, by the human Dicer enzyme, a step central to the RNA interference effect on gene expression. These data provide clues to the basis of the toxic effect of CGG-RNA that is thought to occur in fragile X pre-mutation carriers. In addition, RNA hairpins may also account for the stalling of the 40S ribosomal subunit that is thought to contribute to the translation de®cit in fragile X pre-mutation and full mutation alleles.

Indian Journal of Chemistry Sect B Organic Chemistry Including Medical Chemistry, 1998

Polymer Plastics Technology and Engineering, Sep 22, 2006

A number of formulations were developed using urethane diacry-late oligomer in combination with a... more A number of formulations were developed using urethane diacry-late oligomer in combination with a series of monofunctional and multifunctional reactive diluents possessing diverse glass transi-tion temperatures from -50°C to 250°C. Films prepared with these formulations ...

Toxicological Environmental Chemistry, 1997

Different biotic and abiotic factors were found to play a vital role in attenuating metalaxyl res... more Different biotic and abiotic factors were found to play a vital role in attenuating metalaxyl residues in soil. In addition to metalaxyl many other products were found by HPLC and GC‐MS analysis while studying its soil metabolism in presence of natural sunlight. Three compounds were identified and characterized: 2,6‐dimethylaniline, 2,6‐dimethyl‐N‐ethylacetanilide and N‐(2,6‐dimethyl phenyl) alanine methyl ester.

Proceedings of 1994 4th International Conference on Properties and Applications of Dielectric Materials (ICPADM), 2000

... The bulk insulation in a transformer consists of cellulosic material (paper. presslloard and ... more ... The bulk insulation in a transformer consists of cellulosic material (paper. presslloard and transformerboard) and mineral oil. The cellulosic nia-terials and oil insulation used in transfornier degrade with time. ... (41 R. Evans. R. 8. Wearne and AF A. Wallis. Jnl. of .4pp. ...

Bjog an International Journal of Obstetrics Gynaecology, 2005

Objectives To compare transvaginal ultrasound measurements of endometrial thickness with direct a... more Objectives To compare transvaginal ultrasound measurements of endometrial thickness with direct anatomical measurements and consider the implications of these findings on clinical practice. Design Prospective observational study using two modalities blinded to each other's findings.

Oxidative medicine and cellular longevity

ABSTRACT

150 RING FINGER-DEPENDENT UBIQUITINATION BY PRAJA IS DEPENDENT ON TGF-BETA AND POTENTIALLY DEFINE... more 150 RING FINGER-DEPENDENT UBIQUITINATION BY PRAJA IS DEPENDENT ON TGF-BETA AND POTENTIALLY DEFINES THE FUNCTIONAL STATUS OF THE TUMOR SUPPRESSOR ELF IN HEPATOCELLULAR CANCER. Lopa Mishra, Tapas Saha, Bibhuti Mishra, Eugene Volpe, Yi Tang, Varalakshmi Katuri, Wilma Jogunoori, Deena Vardhini, Georgetown University, Washington, DC; Dale Haines, Temple University, Philadelphia, PA; Xuan Zhou, Ian Gallicano, Richard Schlegel. Georgetown University, Washington, DC. The TGF-b superfamily plays diverse and essential roles in cell differentiation and liver development, as well as in both suppression and formation of hepatocellular carcinoma (HCC). Precise modulation of TGF-b is through Smad activation by the type I receptors, and is dependent upon adaptor proteins such as ELF, a b-spectrin as well as modifying E-3 ligases such as SMURFs and PRAJA. Interestingly nearly two thirds of elf+/- mutant mice develop hepatocellular carcinoma spontaneously at 12-15 months. PRAJA is expressed in abunda...

T1667 Novel Therapeutic Targets for Gastrointestinal Cancer Eugene A. Volpe, Tapas Saha, Will J. ... more T1667 Novel Therapeutic Targets for Gastrointestinal Cancer Eugene A. Volpe, Tapas Saha, Will J. Ferguson, Yi Tang, Varalakshmi Katuri, Wilma Jogunoori, Tiffany M. Blake, Bubhuti Mishra, Lopa Mishra, Stephen R.T. Evans The TGF-β superfamily plays an important role in the formation of gastrointestinal carcinoma, cell differentiation, tumor suppression and liver development. The TGF-β pathway is inactivated in most gastrointestinal cancers. TGF-β is modulated through Smad activation and is dependent upon adaptor proteins such as ELF, a β-spectrin as well as modifying E3 ligases such as PRAJA. We have shown that disruption of the Smad4 adaptor protein ELF, a β-spectrin, disrupts TGF-β signaling. Elf-/- mice die in midgestation from gastrointestinal, liver, neural and heart defects. Aim: To identify new therapeutic targets to control gastrointestinal cancer when the TGF-β signaling pathway is inactivated. Methods and Results: 1. We performed protein kinase assays and microarray analysis...

T1624 TGF-β Modulates Ubiquitination of Tumor Suppressor, ELF, and SMAD3, by Praja, An E3 Ligase,... more T1624 TGF-β Modulates Ubiquitination of Tumor Suppressor, ELF, and SMAD3, by Praja, An E3 Ligase, That Control Hepatocellular Cancer Tapas Saha, Varalakshmi Katuri, Hye Baek, Sang S. Kim, Yi Tang, Wilma Jogunoori, Eugene A. Volpe, Bibhuti Mishra, Lopa Mishra The TGF-β superfamily plays essential roles in cell differentiation and liver development, as well as in both suppression and formation of hepatocellular carcinoma (HCC). TGF-β is modulated through Smad activation and is dependent upon adaptor proteins such as ELF, a â-spectrin as well as modifying E3 ligases such as PRAJA. Interestingly nearly two thirds of elf+/- mutant mice develop hepatocellular carcinoma spontaneously at 12-15 months. PRAJA is expressed in abundance in HCC and is an E3 ligase regulated by TGF-β and BMPs. Aims: To analyze molecular interactions between ELF, Smad3 and PRAJA in TGF-β/BMP signaling pathway in both normal liver formation and in HCC. Methods and Results: 1. PRAJA is expressed in hepatocyte progen...

1098 IDENTIFICATION OF MOLECULAR TARGETS FOR HEPATOCELLULAR CANCER AND ELF PHOSPHORYLATION BY TGF... more 1098 IDENTIFICATION OF MOLECULAR TARGETS FOR HEPATOCELLULAR CANCER AND ELF PHOSPHORYLATION BY TGF-BETA RECEPTOR I IN HEPATOCELLULAR CARCINOMA. Eugene A. Volpe1, Tapas Saha1, Yi Tang1, Bibhuti Mishra1, Lopa Mishra1,2, Lynt B. Johnson1, Stephen RT Evans1; 1Departments of Surgical Sciences, Medicine, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC; 2Department of Veterans Affairs Medical Center, Washington, DC. BACKGROUND: Transforming growth factor beta (TGF-b) signaling through Smad proteins is involved in regulation of cell growth, differentiation and lineage in a wide variety of tissues (Mishra et al., 2005). Smad modulation is dependent upon adaptor proteins and E3 ligases. Differential expression of PRAJA and ELF (embryonic liver fodrin) in hepatocellular cancer cells (HCC) and disruption of ELF, a Smad4 adaptor protein, inactivates TGF-b signaling in elf+/- mutant mice that develop hepatocellular cancers (Tang et al., 2003). PRAJA is a novel RING fing...

153 TGF-β PATHWAY MEMBERS SMAD3 AND ELF ARE KEY REGULATORS OF HEPATOCELLULAR CANCERS Young Woo Ki... more 153 TGF-β PATHWAY MEMBERS SMAD3 AND ELF ARE KEY REGULATORS OF HEPATOCELLULAR CANCERS Young Woo Kim1, Peter Kreishman2, Chohee Yun1, Wilma Jogunoori1, Eugene A. Volpe1, Tapas Saha1, Jonathan S. Mendelson1, Tiffany M. Blake1, Michael J. Pishvaian1, Yi Tang1, Bibhuti Mishra1, Lopa Mishra1,2; 1Surgery, Georgetown University, Washington, DC; 2DVAMC, Washington, DC The transforming growth factor-β (TGF-β) pathway constitutes a central signaling network that plays an essential role in cell differentiation, proliferation, motility, apoptosis and tumorigenesis. TGF-β signals are conveyed through type I/II receptors to specific intracellular mediators known as SMAD. Activation of SMAD3, a receptor activated SMAD, results in nuclear translocation and activation of target genes. We have shown that the adaptor protein ELF plays a key role in TGF-β signaling through SMAD3 and SMAD4 (Science, 2003, 299:574-577). Further analysis has revealed that over 40% of elf+/- mice spontaneously develop hepat...

2013 IEEE International Conference on Industrial Technology (ICIT), 2013