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Architecture, Assembly and Dynamics of Molecular Machines Regulating Eukaryotic Gene Transcription

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Air date: Wednesday, January 30, 2013, 3:00:00 PM
Time displayed is Eastern Time, Washington DC Local
Views: Total views: 436, (101 Live, 335 On-demand)
Category: WALS - Wednesday Afternoon Lectures
Runtime: 01:06:39
Description: Wednesday Afternoon Lecture Series

The regulation of gene expression is a complex task that is critical for the growth, development, and survival of organisms. Dr. Nogales’ lecture will describe structural studies concerning protein complexes involved on epigenetic gene silencing and transcription initiation.

Polycomb Repressive Complex 2 (PRC2) is essential for gene silencing, establishing transcriptional repression of specific genes by tri-methylating Lysine 27 of histone H3, which eventually results in the compaction of chromatin and the inaccessibility of genes to the transcriptional machinery. Dr. Nogales’ group has obtained the first three-dimensional structure of the human PRC2 complex bound to its cofactor AEBP2 and localized all the PRC2 subunits and their functional domains, generating a detailed map of interactions. They show that regions in PRC2 that interact with modified histone tails are localized near the methyltransferase site, suggesting a molecular mechanism for the chromatin-based regulation of PRC2 activity.

A highly regulated step in gene expression (in non-compacted chromatin) is the initiation of transcription by RNA polymerase II, which requires basal transcription factors known as TFIIA, TFIIB, TFIID, TFIIE, TFIIF, and TFIIH. These factors assemble sequentially onto the core promoters of protein coding genes to form a transcription pre-initiation complex following the initial recruitment of TFIID to core promoter DNA sequences. The size and scarcity of TFIID, typically purified from endogenous sources, are bottlenecks for structural studies. They have applied single-particle EM and extensive image-sorting methodologies to characterize the structural dynamics of human TFIID. We found a novel “rearranged” conformation of TFIID that corresponds to a high-affinity DNA binding state. Their studies suggest a model in which the distinct conformations of TFIID may serve as targets for transcription factors/cofactors to regulate the recruitment of TFIID to specific core promoters and the final transcriptional output. They have also used an in vitro reconstituted system to study the stepwise assembly of human TBP (substituting for TFIID), TFIIA, TFIIB, Pol II, TFIIF, TFIIE, and TFIIH onto promoter DNA using cryo-electron microscopy. Their structural analyses provide pseudo-atomic models at various stages of transcription initiation that illuminate critical molecular interactions for the proper loading of the transcription start site at the active center of Pol II.
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NLM Title: Architecture, assembly and dynamics of molecular machines regulating eukaryotic gene transcription / Eva Nogales.
Author: Nogales, Eva.
National Institutes of Health (U.S.),
Publisher:
Abstract: (CIT): The regulation of gene expression is a complex task that is critical for the growth, development, and survival of organisms. Dr. Nogales" lecture will describe structural studies concerning protein complexes involved on epigenetic gene silencing and transcription initiation. Polycomb Repressive Complex 2 (PRC2) is essential for gene silencing, establishing transcriptional repression of specific genes by tri-methylating Lysine 27 of histone H3, which eventually results in the compaction of chromatin and the inaccessibility of genes to the transcriptional machinery. Dr. Nogales" group has obtained the first three-dimensional structure of the human PRC2 complex bound to its cofactor AEBP2 and localized all the PRC2 subunits and their functional domains, generating a detailed map of interactions. They show that regions in PRC2 that interact with modified histone tails are localized near the methyltransferase site, suggesting a molecular mechanism for the chromatin-based regulation of PRC2 activity. A highly regulated step in gene expression (in non-compacted chromatin) is the initiation of transcription by RNA polymerase II, which requires basal transcription factors known as TFIIA, TFIIB, TFIID, TFIIE, TFIIF, and TFIIH. These factors assemble sequentially onto the core promoters of protein coding genes to form a transcription pre-initiation complex following the initial recruitment of TFIID to core promoter DNA sequences. The size and scarcity of TFIID, typically purified from endogenous sources, are bottlenecks for structural studies. They have applied single-particle EM and extensive image-sorting methodologies to characterize the structural dynamics of human TFIID. We found a novel "rearranged" conformation of TFIID that corresponds to a high-affinity DNA binding state. Their studies suggest a model in which the distinct conformations of TFIID may serve as targets for transcription factors/cofactors to regulate the recruitment of TFIID to specific core promoters and the final transcriptional output. They have also used an in vitro reconstituted system to study the stepwise assembly of human TBP (substituting for TFIID), TFIIA, TFIIB, Pol II, TFIIF, TFIIE, and TFIIH onto promoter DNA using cryo-electron microscopy. Their structural analyses provide pseudo-atomic models at various stages of transcription initiation that illuminate critical molecular interactions for the proper loading of the transcription start site at the active center of Pol II.
Subjects: Eukaryotic Cells--physiology
Gene Expression Regulation--physiology
Molecular Structure
Publication Types: Lecture
Webcast
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NLM Classification: QU 475
NLM ID: 101601869
CIT Live ID: 12297
Permanent link: https://videocast.nih.gov/watch=12297