Bachelor of Science, University of Michigan Ann Arbor (2008)
Doctor of Philosophy, University of North Carolina, Chapel Hill (2014)
Paul Khavari, Postdoctoral Faculty Sponsor
The YEATS domain, found in a number of chromatin-associated proteins, has recently been shown to have the capacity to bind histone lysine acetylation. Here, we show that the YEATS domain of Taf14, a member of key transcriptional and chromatin-modifying complexes in yeast, is a selective reader of histone H3 Lys9 acetylation (H3K9ac). Structural analysis reveals that acetylated Lys9 is sandwiched in an aromatic cage formed by F62 and W81. Disruption of this binding in cells impairs gene transcription and the DNA damage response. Our findings establish a highly conserved acetyllysine reader function for the YEATS domain protein family and highlight the significance of this interaction for Taf14.
View details for DOI 10.1101/gad.269977.115
View details for PubMedID 26341557
Histones and their posttranslational modifications (PTMs) play an important role in regulating DNA-templated processes. While some PTMs directly modulate chromatin architecture via charge effects, others rely on the action of reader or effector proteins that can recognize and bind the modification to fulfill distinct cellular outcomes. One PTM that has been well studied with regard to reader proteins is histone lysine methylation - a PTM linked to many DNA-templated processes including transcription, DNA replication and DNA repair. In this review, we summarize the current understanding of how histone lysine methylation is read during the process of active transcription. We also describe how the interpretation of lysine methylation fits into a larger, more complex 'code' of histone PTMs to modulate chromatin structure and function. These insights take into account emerging concepts in the field in an effort to help facilitate future studies.
View details for DOI 10.1016/j.bbagrm.2014.03.002
View details for Web of Science ID 000347129100002
View details for PubMedID 24631869
Monoubiquitylation of histone H2B on Lys123 (H2BK123ub1) plays a multifaceted role in diverse DNA-templated processes, yet the mechanistic details by which this modification is regulated are not fully elucidated. Here we show in yeast that H2BK123ub1 is regulated in part through the protein stability of the E3 ubiquitin ligase Bre1. We found that Bre1 stability is controlled by the Rtf1 subunit of the polymerase-associated factor (PAF) complex and through the ability of Bre1 to catalyze H2BK123ub1. Using a domain in Rtf1 that stabilizes Bre1, we show that inappropriate Bre1 levels lead to defects in gene regulation. Collectively, these data uncover a novel quality control mechanism used by the cell to maintain proper Bre1 and H2BK123ub1 levels, thereby ensuring proper control of gene expression.
View details for DOI 10.1101/gad.243121.114
View details for Web of Science ID 000339880200003
View details for PubMedID 25085417
Widespread changes in gene expression underlie B cell development and activation, yet our knowledge of which chromatin-remodeling factors are essential is limited. Here, we demonstrate that the BRG1 catalytic subunit of SWI/SNF complexes was dispensable for murine B cell development but played an important, albeit selective, role during activation. Although BRG1 was dispensable for CD69 induction and differentiation into plasma cells based on the ability of mutant B cells to undergo hypertrophy and secrete IgM antibodies, it was required for robust cell proliferation in response to activation. Accordingly, BRG1 was required for only ?100 genes to be expressed at normal levels in na´ve B cells but >1,000 genes during their activation. BRG1 upregulated fivefold more genes than it downregulated, and the toll-like receptor pathway and JAK/STAT cytokine-signaling pathways were particularly dependent on BRG1. The importance of BRG1 in B cell activation was underscored by the occurrence of opportunistic Pasteurella infections in conditionally mutant mice. B cell activation has long served as a model of inducible gene expression, and the results presented here identify BRG1 as a chromatin-remodeling factor that upregulates the transcriptome of B cells during their activation to promote rapid cell proliferation and to mount an effective immune response.
View details for DOI 10.1002/jcp.24414
View details for Web of Science ID 000327883100007
View details for PubMedID 23757284
Bypass of Ess1 (Bye1) is a nuclear protein with a domain resembling the central domain in the transcription elongation factor TFIIS. Here we show that Bye1 binds with its TFIIS-like domain (TLD) to RNA polymerase (Pol) II, and report crystal structures of the Bye1 TLD bound to Pol II and three different Pol II-nucleic acid complexes. Like TFIIS, Bye1 binds with its TLD to the Pol II jaw and funnel. In contrast to TFIIS, however, it neither alters the conformation nor the in vitro functions of Pol II. In vivo, Bye1 is recruited to chromatin via its TLD and occupies the 5'-region of active genes. A plant homeo domain (PHD) in Bye1 binds histone H3 tails with trimethylated lysine 4, and this interaction is enhanced by the presence of neighboring posttranslational modifications (PTMs) that mark active transcription and conversely is impaired by repressive PTMs. We identify putative human homologs of Bye1, the proteins PHD finger protein 3 and death-inducer obliterator, which are both implicated in cancer. These results establish Bye1 as the founding member of a unique family of chromatin transcription factors that link histones with active PTMs to transcribing Pol II.
View details for DOI 10.1073/pnas.1311010110
View details for Web of Science ID 000324495300041
View details for PubMedID 24003114
The tRNA gene-mediated (tgm) silencing of RNA polymerase II promoters is dependent on subnuclear clustering of the tRNA genes, but genetic analysis shows that the silencing requires additional mechanisms. We have identified proteins that bind tRNA gene transcription complexes and are required for tgm silencing but not required for gene clustering. One of the proteins, Mod5, is a tRNA modifying enzyme that adds an N6-isopentenyl adenosine modification at position 37 on a small number of tRNAs in the cytoplasm, although a subpopulation of Mod5 is also found in the nucleus. Recent publications have also shown that Mod5 has tumor suppressor characteristics in humans as well as confers drug resistance through prion-like misfolding in yeast. Here, we show that a subpopulation of Mod5 associates with tRNA gene complexes in the nucleolus. This association occurs and is required for tgm silencing regardless of whether the pre-tRNA transcripts are substrates for Mod5 modification. In addition, Mod5 is bound to nuclear pre-tRNA transcripts, although they are not substrates for the A37 modification. Lastly, we show that truncation of the tRNA transcript to remove the normal tRNA structure also alleviates silencing, suggesting that synthesis of intact pre-tRNAs is required for the silencing mechanism. These results are discussed in light of recent results showing that silencing near tRNA genes also requires chromatin modification.
View details for DOI 10.1073/pnas.1219946110
View details for Web of Science ID 000323069200010
View details for PubMedID 23898186