Our group has continued studies of chromatin structure and the regulation of eukaryotic gene expression. We have made significant progress towards understanding the mechanism of ATP-dependent chromatin remodeling by Drosophila NURF (Nucleosome Remodeling Factor). To elucidate the biological significance of NURF-induced nucleosome sliding, we have isolated mutations for Drosophila nurf301. We confirm that NURF is required for transcription activation in vivo. In nurf301 mutants, heat-shock transcription factor binding to and transcription of the hsp70 and hsp26 genes are impaired. Additionally, NURF is required for homeotic gene expression. Consistent with this, nurf301 mutants recapitulate phenotypes of Enhancer of bithorax, a positive regulator of the Bithorax-Complex previously localized to the same genetic interval. Finally, mutants in NURF subunits exhibit neoplastic transformation of larval blood cells that induces melanotic tumor formation. These results reveal that NURF is required not only for proper regulation of genes involved in the stress response and development, but also for tumor suppression. We are also making excellent progress on studies of INO80, a member of the SWI2/SNF2 superfamily. We have completed identification of all subunits by mass spectrometry, and are conducting genetic and biochemical experiments to elucidate the mechanism and physiological functions of the complex. The INO80 complex contains stoichiometric amounts of actin and three actin related proteins (Arp4, Arp5, and Arp8). Arp4 and actin are essential for cell survival, but the viability of null mutants for Arp5 and Arp8 allowed us to further investigate their functional roles. We uncovered functions of Arp5 and Arp8 in chromatin remodeling by biochemical analysis of the null mutants. Purification of INO80 complexes from arp5D and arp8D cells showed that the mutant complexes are compromised for DNA binding, nucleosome mobilization, and Ino80 ATPase activity. Consistent with the biochemical findings, arp5D and arp8D mutants show phenotypes similar to ino80D. These results provide new insights on the role of actin and Arps in the cell nucleus. longstanding reports of actin in the cell nucleus.

Agency
National Institute of Health (NIH)
Institute
Division of Basic Sciences - NCI (NCI)
Type
Intramural Research (Z01)
Project #
1Z01BC005263-22
Application #
6949797
Study Section
(LMCB)
Project Start
Project End
Budget Start
Budget End
Support Year
22
Fiscal Year
2003
Total Cost
Indirect Cost
Name
Basic Sciences
Department
Type
DUNS #
City
State
Country
United States
Zip Code
Kwon, So Yeon; Xiao, Hua; Wu, Carl et al. (2009) Alternative splicing of NURF301 generates distinct NURF chromatin remodeling complexes with altered modified histone binding specificities. PLoS Genet 5:e1000574
Wu, Wei-Hua; Wu, Chwen-Huey; Ladurner, Andreas et al. (2009) N terminus of Swr1 binds to histone H2AZ and provides a platform for subunit assembly in the chromatin remodeling complex. J Biol Chem 284:6200-7
Luk, Ed; Vu, Ngoc-Diep; Patteson, Kem et al. (2007) Chz1, a nuclear chaperone for histone H2AZ. Mol Cell 25:357-68
Mizuguchi, Gaku; Xiao, Hua; Wisniewski, Jan et al. (2007) Nonhistone Scm3 and histones CenH3-H4 assemble the core of centromere-specific nucleosomes. Cell 129:1153-64
Schwanbeck, Ralf; Xiao, Hua; Wu, Carl (2004) Spatial contacts and nucleosome step movements induced by the NURF chromatin remodeling complex. J Biol Chem 279:39933-41
Mizuguchi, Gaku; Shen, Xuetong; Landry, Joe et al. (2004) ATP-driven exchange of histone H2AZ variant catalyzed by SWR1 chromatin remodeling complex. Science 303:343-8
Shen, Xuetong; Xiao, Hua; Ranallo, Ryan et al. (2003) Modulation of ATP-dependent chromatin-remodeling complexes by inositol polyphosphates. Science 299:112-4
Shen, Xuetong; Ranallo, Ryan; Choi, Eugene et al. (2003) Involvement of actin-related proteins in ATP-dependent chromatin remodeling. Mol Cell 12:147-55