Michael Hampsey Professor Robert Wood Johnson Medical School Dept. of Biochemistry Research & Public Health Building. Room 285 Piscataway. NJ 08854 (732) 235-5888 FAX - 5889 hampsemi@umdnj.edu Visit Dr. Hampsey's Lab

Gene expression. chromatin. yeast genetics

Our laboratory studies the regulation of gene expression in eukaryotic organisms. We are especially interested in transcription of protein-encoding genes by RNA polymerase II (Pol II). The experimental organism used in most of our work is the yeast Saccharomyces cerevisiae, which enables us to use a powerful combination of classical genetics, molecular biology and modern biochemistry in our research. Our current efforts are focused on two questions: 1) How is the transcription coupled to RNA processing? and 2) How do gene loops that juxtapose the 3’-end of the gene with the promoter affect the mechanism and regulation of gene expression?

1) Coupling of 3' end processing to Pol II transcription. Nascent mRNA undergoes modifications that include 5' capping, splicing, 3' endonucleolytic cleavage and polyadenylation. These processing events occur co-transcriptionally and involve recruitment and exchange of processing enzymes to the C-terminal domain (CTD) of the Rpb1 subunit of Pol II. The CTD is phosphorylated and dephosphorylated at Ser2 and Ser5 during the transcription cycle. We recently discovered that the Ssu72 protein is an integral component of the CPF 3' end processing complex and is a CTD Ser5-P phosphatase. We are now focused on (i) determining how Ssu72-mediated Ser5-P dephosphorylation affects Pol II progression through the transcription cycle; (ii) how Ssu72 is regulated by the transcriptional machinery; and (iii) how Ssu72 is regulated by 3' end processing factors. These questions are being addressed in collaboration with Professor Claire Moore (Tufts Medical School).

2) Role of “gene loops” in transcription. Although Ssu72 is a component of the CPF 3' end processing complex, we first identified this protein based on genetic and physical interactions with TFIIB, a transcription initiation factor. As such, Ssu72 defined an unexpected link between the Pol II initiation and termination machineries. This suggested to us that the ends of gene might physically interact to form gene loops. Our recent studies revealed that gene loops are a general feature of Pol II transcription. Looping is dependent upon transcription and requires specific components of the transcription initiation and 3’-end processing complexes, including the Ssu72 CTD phosphatase. We are now working (i) to define the factors and mechanisms involved in loop formation; and (ii) to determine the functional significance of gene loops with respect to regulation of gene expression.

A remarkable feature of Pol II transcription and mRNA processing is the extent to which these two coupled processes – and the proteins that facilitate them – are conserved among eukaryotic organisms. Accordingly, we are able to exploit the extensive arsenal of experimental approaches available in yeast with the results directly applicable to human biology and medicine.

Selected Publications

Krishnamurthy S, Ghazy MA, Moore C, Hampsey M. (2009) Functional interaction of the Ess1 prolyl isomerase with components of the RNA polymerase II initiation and termination machineries. Mol Cell Biol. 29(11):2925-34.

Singh BN, Ansari A, Hampsey M. (2009) Detection of gene loops by 3C in yeast. Methods. 48(4):361-7.

Krishnamurthy S, Ghazy MA, Moore C, Hampsey M. (2009) Functional interaction of the Ess1 prolyl isomerase with components of the RNA polymerase II initiation and termination machineries. Mol Cell Biol. 29(11):2925-34.

Krishnamurthy S, Hampsey M. (2009) Eukaryotic transcription initiation. Curr Biol. 19(4):R153-6.

Ghazy MA, He X, Singh BN, Hampsey M, Moore C. (2009) The essential N terminus of the Pta1 scaffold protein is required for snoRNA transcription termination and Ssu72 function but is dispensable for pre-mRNA 3'-end processing. Mol Cell Biol. 29(8):2296-307.

Estrella LA, Krishnamurthy S, Timme CR, Hampsey M. (2008) The Rsp5 E3 ligase mediates turnover of low affinity phosphate transporters in Saccharomyces cerevisiae. J Biol Chem. 283(9):5327-34.

Hampsey M, Kinzy TG. (2007) Synchronicity: policing multiple aspects of gene expression by Ctk1. Genes Dev. 21(11):1288-91.

Singh, B. N. and M. Hampsey (2007) A transcription-independent role for TFIIB in gene looping. Mol. Cell 27:806-816.

Reyes-Reyes, M. and Hampsey, M. (2007) Role for the Ssu72 C-terminal domain phosphatase in RNA polymerase II transcription elongation. Mol. Cell. Biol. 27:926-936.

Hampsey, M. (2006) The RNA polymerase II initiation complex: looking for a place to start. Nat. Struct. Mol. Biol. 13:564-566.

Ansari, A. and Hampsey, M. (2005) A role for the CPF 3’-end processing machinery in RNAP II-dependent gene looping. Genes & Dev. 19:2969-2978.

Krishnamurthy, S., He, X., Reyes-Reyes, M., Moore, C. and Hampsey, M. (2004) Ssu72 is a RNA polymerase II CTD phosphatase. Mol. Cell 14:387-394.

Chen, B.-S. and Hampsey, M. (2004) Functional interaction between TFIIB and the Rpb2 subunit of RNA polymerase II: implications for the mechanism of transcription start site selection. Mol. Cell Biol. 24:3983-3991.

Hampsey, M. and Reinberg, D. (2003) Tails of intrigue: phosphorylation of RNA polymerase II mediates histone methylation. Cell 113:429-432.

He, X., Khan, A.U., Cheng, H., Pappas, D.L., Hampsey, M. and Moore, C.L. (2003) Functional interactions between the transcription and mRNA 3' end processing machineries mediated by Ssu72 and Sub1. Genes Dev. 17:1030-1042.