In JoVE (1)

Other Publications (5)

Articles by Alfredo J. Hernandez in JoVE

Other articles by Alfredo J. Hernandez on PubMed

Interventional EUS-guided Cholangiography: Evaluation of a Technique in Evolution

Gastrointestinal Endoscopy. Jul, 2006  |  Pubmed ID: 16813803

Interventional EUS-guided cholangiography (IEUC) has been increasingly used as an alternative to percutaneous transhepatic cholangiography (PTC) in cases of biliary obstruction when ERCP is unsuccessful.

EUS-guided Pancreaticogastrostomy: Analysis of Its Efficacy to Drain Inaccessible Pancreatic Ducts

Gastrointestinal Endoscopy. Feb, 2007  |  Pubmed ID: 17141775

EUS-guided pancreaticogastrostomy (EPG) has been reported as an alternative to surgery in cases of pancreatic stricture where ERCP is unsuccessful.

Regulatory Interactions Between RNA and Polycomb Repressive Complex 2

Molecular Cell. Jul, 2014  |  Pubmed ID: 24882207

Polycomb repressive complex 2 (PRC2) is a histone methyltransferase that is localized to thousands of mammalian genes. Though important to human disease and as a drug target, how PRC2 is recruited remains unclear. One model invokes cis-regulatory RNA. Herein, we biochemically and functionally probe PRC2's recognition of RNA using the X-inactivation model. We observe surprisingly high discriminatory capabilities. While SUZ12 and JARID2 subunits can bind RNA, EZH2 has highest affinity and is somewhat promiscuous. EED regulates the affinity of EZH2 for RNA, lending greater specificity to PRC2-RNA interactions. Intriguingly, while RNA is crucial for targeting, RNA inhibits EZH2's catalytic activity. JARID2 weakens PRC2's binding to RNA and relieves catalytic inhibition. We propose that RNA guides PRC2 to its target but inhibits its enzymatic activity until PRC2 associates with JARID2 on chromatin. Our study provides a molecular view of regulatory interactions between RNA and PRC2 at the chromatin interface.

Primer Release is the Rate-limiting Event in Lagging-strand Synthesis Mediated by the T7 Replisome

Proceedings of the National Academy of Sciences of the United States of America. May, 2016  |  Pubmed ID: 27162371

DNA replication occurs semidiscontinuously due to the antiparallel DNA strands and polarity of enzymatic DNA synthesis. Although the leading strand is synthesized continuously, the lagging strand is synthesized in small segments designated Okazaki fragments. Lagging-strand synthesis is a complex event requiring repeated cycles of RNA primer synthesis, transfer to the lagging-strand polymerase, and extension effected by cooperation between DNA primase and the lagging-strand polymerase. We examined events controlling Okazaki fragment initiation using the bacteriophage T7 replication system. Primer utilization by T7 DNA polymerase is slower than primer formation. Slow primer release from DNA primase allows the polymerase to engage the complex and is followed by a slow primer handoff step. The T7 single-stranded DNA binding protein increases primer formation and extension efficiency but promotes limited rounds of primer extension. We present a model describing Okazaki fragment initiation, the regulation of fragment length, and their implications for coordinated leading- and lagging-strand DNA synthesis.

Destabilization of B2 RNA by EZH2 Activates the Stress Response

Cell. Dec, 2016  |  Pubmed ID: 27984727

More than 98% of the mammalian genome is noncoding, and interspersed transposable elements account for ∼50% of noncoding space. Here, we demonstrate that a specific interaction between the polycomb protein EZH2 and RNA made from B2 SINE retrotransposons controls stress-responsive genes in mouse cells. In the heat-shock model, B2 RNA binds stress genes and suppresses their transcription. Upon stress, EZH2 is recruited and triggers cleavage of B2 RNA. B2 degradation in turn upregulates stress genes. Evidence indicates that B2 RNA operates as a "speed bump" against advancement of RNA polymerase II, and temperature stress releases the brakes on transcriptional elongation. These data attribute a new function to EZH2 that is independent of its histone methyltransferase activity and reconcile how EZH2 can be associated with both gene repression and activation. Our study reveals that EZH2 and B2 together control activation of a large network of genes involved in thermal stress.

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