Regulation of chromatin structure and gene expression by H3S10 phosphorylation

Iowa State University, Ames IA

Investigators

Abstract

Regulation of the levels and timing of expression can vary significantly between different types of genes. For example, “housekeeping” or “constitutive” genes carrying out normal maintenance functions are, typically, expressed broadly at consistent levels whereas genes involved in more dynamic processes such as development, stress-response, or immune-related functions have more complex timing and expression level requirements, and often require considerable “fine-tuning” for proper function. It has been shown that gene expression levels can be regulated by enzymes known as “histone writers” that mark the chromatin with activating or repressing marks, but how these enzymes collaborate to effect dynamic rheostat control is poorly understood. This project will explore how three different histone writers coordinate to fine-tune gene expression, determine how this marking affects chromatin accessibility, and identify factors involved in opening or condensing the chromatin. Some of these experiments will be incorporated into independent undergraduate research projects, including as part of a new departmental summer intern program directed by the PI that integrates conducting scientific research projects with developing presentation skills. The hypothesis that histone modifications H3K9me2, H3S10ph, and H4K16ac “fine-tune” gene expression in a coordinated fashion by regulating the permissiveness of the chromatin state for transcription will be tested. Interphase, Drosophila 3rd instar larval salivary glands are uniquely suited for these studies, given the lack of interference from residual mitotic H3S10 phosphorylation. Also, investigators will test whether the three epigenetic mark writers (Su(var)3-9, JIL-1, and MOF) directly regulate each other via post-translational modifications. This will be accomplished using two approaches: 1) wild-type and mutated lacI or GAL-4 fusion constructs for the epigenetic writers JIL-1 H3S10 kinase, Su(var)3-9 H3K9 methyltransferase and MOF H4K16 acetyltransferase will be targeted to different chromatin locations (individually or sequentially) and molecularly characterized with respect to induced changes in epigenetic marking and chromatin structure, recruitment or loss of chromatin remodeling factors, nucleosome array organization, and reporter gene expression; and 2) histone writer crossregulation will be studied by mutating known JIL-1 phosphorylation sites on Su(var)3-9 and potential MOF-1 acetylation sites on JIL-1 and characterizing their subsequent effects on chromatin structure. These studies will assess the special relationship between H3K9me2 and H3S10ph in the relatively unexplored genomic context of euchromatic gene regulation. This project is co-funded by the Genetic Mechanisms program in BIO/MCB and by the Estab­lished Program to Stim­u­late Com­pet­i­tive Research (EPSCoR) Program in the Office of Integrative Activities. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.