Gender	Male
E-mail	brehon.laurent@mssm.edu
Education and Training	Ph.D., Massachusetts Institute of Technology
	A.B., Bowdoin College
	Fellowship, Columbia University
Awards	2002 State University of New York Chancellor??s Research Award
	1993 Basil O'Connor Starter Scholar Research Award March of Dimes Birth Defects Foundation
	1988 Individual National Research Service Award National Institutes of Health

Education and Training	Ph.D., Massachusetts Institute of Technology
	A.B., Bowdoin College
	Fellowship, Columbia University

Chromosome dynamics during the processes of chromosome segregation, the maintenance of genome integrity, and gene transcription

Our laboratory studies how dynamic changes in chromatin structure regulate the fundamental cellular events of chromosome segregation, DNA damage repair, and gene transcription. In particular, we study the mechanisms by which RSC and Swi/Snf, two conserved ATP-utilizing chromatin-remodeling complexes, control these processes. Defects in the remodeling of chromatin can lead to cancers and severe genetic diseases, and human SWI/SNF counterpart proteins have been shown to function as powerful tumor suppressors. We use the simple eukaryote Saccharomyces cerevisiae as the model system and will extend these experiments in mammalian cells.

Studies in our laboratory established a key role for the RSC chromatin-remodeling activity in regulating chromatin folding during genomic transmission. We found that RSC's remodeling activity is required for the function of the centromere-kinetochore (Hsu et al. 2003), the region of the chromosome that is responsible for segregating sister chromatids to daughter cells during cell division. More recently,we've shown that RSC facilitates the loading of cohesin onto the arms of newly replicated sister chromatids (Huang et al. 2004; Figs. 1 and 2). Future experiments will test RSC's role in establishing and/or maintaining the cohesion and condensation of sister chromatids for proper partitioning.

The accurate and efficient repair of the ~10⁴ DNA damage events per day for a mammalian cell are essential for survival; unrepaired DNA lesions disrupt chromosomal integrity and can result in cancers. Moreover, such lesions must be repaired in the context of chromatin. Recent experiments suggest novel roles for both RSC and Swi/Snf in processing DNA double-strand breaks (DSBs) (Chai et al. 2005; Fig. 3). Current efforts are directed towards defining how these ATP-dependent remodelers contribute to the chromatin dynamics required to maintain genome integrity. Translational experiments in mammalian cells will explore roles of the SWI/SNF orthologs in partitioning and repairing the genome during the cell cycle, providing insight into their roles in tumorigenesis.

In another study, we have uncovered a rapid, biphasic response mechanism that relies on the coordinated recruitment of Swi/Snf and histone acetyltransferase activities (Fig. 4). Future experiments will examine at the molecular level how the chromatin-modifying activities are regulated as well as how these phases communicate to properly regulate transcription.

Huang J, Liang B, Qiu J, Laurent BC. ATP-dependent chromatin-remodeling complexes in DNA double-strand break repair: remodeling, pairing, and (re)pairing. Cell Cycle 2005;(4): 1713-1715.

Wong LY, Recht J, Laurent BC. Chromatin remodeling and repair of DNA double-strand breaks. J. Mol. Histol. 2006;(37): 261-269.

Liang B, Qiu J, Ratnakumar K, Laurent BC. RSC functions as an early double-strand break sensor in the cell's response to DNA damage. Curr. Biol. 2007;(17): 1432-1437.

Cairns BR, Lorch Y, Li Y, Zhang M, Lacomis L, Erdjument-Bromage H, Tempst P, Du J, Laurent BC, Kornberg RD. RSC, an essential, abundant chromatin-remodeling complex. Cell 1996 Dec; 87(7): 1249-1260.

Cao Y, Cairns BR, Kornberg RD, Laurent BC. Sfh1p, a component of a novel chromatin-remodeling complex, is required for cell cycle progression. Mol Cell Biol 1997 Jun; 17(6): 3323-3334.

Du J, Nasir I, Benton BK, Kladde MP, Laurent BC. Sth1p, a Saccharomyces cerevisiae Snf2p/Swi2p homolog, is an essential ATPase in RSC and differs from Snf/Swi in its interactions with histones and chromatin-associated proteins. Genetics 1998 Nov; 150(3): 987-1005.

Sudarsanam P, Cao Y, Wu L, Laurent BC, Winston F. The nucleosome remodeling complex, Snf/Swi, is required for the maintenance of transcription in vivo and is partially redundant with the histone acetyltransferase, Gcn5. EMBO J 1999 Jun; 18(11): 3101-3106.

Geng F, Cao Y, Laurent BC. Essential roles of Snf5p in Snf-Swi chromatin remodeling in vivo. Mol Cell Biol 2001 Jul; 21(13): 4311-4320.

Hsu JM, Huang J, Meluh PB, Laurent B. The yeast RSC chromatin-remodeling complex is required for kinetochore function in chromosome segregation. Mol Cell Biol 2003 May; 23(9): 3202-3215.

Huang J, Laurent BC. A Role for the RSC chromatin remodeler in regulating cohesion of sister chromatid arms. Cell Cycle 2004 Aug; 3(8): 973-975.

Huang J, Hsu JM, Laurent BC. The RSC nucleosome-remodeling complex is required for Cohesin's association with chromosome arms. Mol Cell 2004 Mar; 13(5): 739-750.

Geng F, Laurent BC. Roles of SWI/SNF and HATs throughout the dynamic transcription of a yeast glucose-repressible gene. EMBO J 2004 Jan; 23(1): 127-137.

Chai B, Huang J, Cairns BR, Laurent BC. Distinct roles for the RSC and Swi/Snf ATP-dependent chromatin remodelers in DNA double-strand break repair. Genes Dev 2005 Jul; 19(14): 1656-1661.