Dr. Gregory M. Gilmartin
Our work focuses on the processing of RNA polymerase II transcripts in higher eukaryotes. The central goal of our work is to understand the nature of the processing event that serves to generate the 3′ ends of mature mRNAs and to elucidate the mechanism by which 3′ processing is coupled to RNA polymerase II transcription termination.
The 3′ processing of a primary transcript is an obligatory step in the biosynthesis of a functional message and has been shown to contribute to the regulation of gene expression through the modulation of both the level and coding capacity of the mature message. The 3′ processing of polyadenylated mRNAs entails the endonucleolytic cleavage of the pre-mRNA and the subsequent addition of ~20 adenylate residues. A poly(A) site is defined by two cis-acting sequences – a highly conserved AAUAAA hexamer 10 – 30 nucleotides upstream of the cleavage site and an amorphous downstream U- or GU-rich element that possesses neither an identifiable consensus sequence nor a conserved secondary structure. Alternative poly(A) site choice may act to expand the coding capacity of an mRNA through the inclusion of additional exons or may act to modulate mRNA stability through the inclusion of specific sequences that mediate mRNA turnover. In addition to its role in the generation of the 3′ end of the mature message, 3′ processing has been shown to be intimately linked to both mRNA splicing and to transcription termination. Thus a knowledge of the biochemistry of mRNA 3′ processing is critical to an understanding of the regulation of gene expression.
Our investigation of the mechanism and regulation of mRNA 3′ processing focuses on the human immunodeficiency virus type 1 (HIV-1). The architecture of the HIV-1 genome presents an intriguing dilemma for the 3’processing of viral transcripts – to disregard a canonical ‘core’ poly(A) site processing signal present at the 5′ end of the transcript and yet to efficiently utilize an identical signal that resides at the 3′ end of the message. The elucidation of the novel mechanism underlying HIV-1 poly(A) site selection is crucial to an understanding of viral replication. Our long term objective is to exploit the unique nature of the HIV-1 poly(A) site processing signal to design an effective antiviral agent.
Brown KM, Gilmartin GM. A mechanism for the regulation of pre-mRNA 3′ processing by human cleavage factor Im. Mol Cell. 2003 Dec;12(6):1467-76.
Venkataraman K, Brown KM, Gilmartin GM. Analysis of a noncanonical poly(A) site reveals a tripartite mechanism for vertebrate poly(A) site recognition. Genes Dev. 2005 Jun 1;19(11):1315-27.
Gilmartin GM.Eukaryotic mRNA 3′ processing: a common means to different ends. Genes Dev. 2005 Nov 1;19(21):2517-21.
Valente ST, Gilmartin GM, Mott C, Falkard B, Goff SP. Inhibition of HIV-1 replication by eIF3f. Proc Natl Acad Sci U S A. 2009 Mar 17;106(11):4071-8.
Valente ST, Gilmartin GM, Venkatarama K, Arriagada G, Goff SP. HIV-1 mRNA 3′ end processing is distinctively regulated by eIF3f, CDK11, and splice factor 9G8. Mol Cell. 2009 Oct 23;36(2):279-89.