Phillip A. Sharp
Massachusetts Institute of Technology
Election Year: 1983
Primary Section: 22, Cellular and Developmental Biology
Membership Type: Member
We are studying the biochemistry and molecular genetics of two processes important in gene regulation: initiation of transcription by RNA polymerase II and splicing of precursors to mRNAs. Mechanisms regulating the expression of eukaryotic genes are being investigated using both biochemistry and molecular genetics. The processes under investigation are: the role of basal factors in initiation of transcription by RNA polymerase II; the mechanism by which sequence-specific DNA binding proteins enhance initiation; the role of the POU domain proteins Oct-1 and Oct-2 and the helix-loop-helix leucine zipper protein TFEB and MYC in B cell development; and the nature of proteins and RNAs which recognize nuclear precursor RNA to regulate or catalyze splicing. The splicing of pre-mRNAs involves the selection of 5' and 3' splice sites for joining by a spliceosome based reaction. The spliceosome contains five small nuclear RNA particles (snRNPs) as well as a large number of proteins. Proteins which recognize specific sequences in the precursor RNA must direct splicing and formation of the spliceosome. Proteins with this activity have not been well analyzed and we are using a combination of mutagenesis and RNA binding assays to identify and purify them. Protein-RNA recognition is also critical in regulation of both splicing and transcription of the AIDS virus HIV- 1. The mechanisms by which the Rev protein stimulates the release into the cytoplasm of unspliced viral RNA through recognition of the Rev-Responsive RNA element and Tat protein stimulates transcription through recognition of the Tat-Responsive RNA element are under investigation.