A Role for the Drosophila SU(VAR)3-9 Protein in Chromatin Organization at the Histone Gene Cluster and in Suppression of Position-Effect Variegation

Corresponding author: Sarbjit S. Ner, University of British Columbia, Vancouver, BC V6T 1Z4, Canada., ner{at}zoology.ubc.ca (E-mail)

Communicating editor: S. HENIKOFF

Mutations in the gene for Su(var)3-9 are dominant suppressors of position-effect variegation (PEV). We show that SU(VAR)3-9 is a chromatin-associated protein and identify the large multicopy histone gene cluster (HIS-C) as one of its target loci. The organization of nucleosomes over the entire HIS-C region is altered in Su(var)3-9 mutants and there is a concomitant increase in expression of the histone genes. SU(VAR)3-9 is a histone H3 methyltransferase and, using chromatin immunoprecipitation, we show that SU(VAR)3-9 is present at the HIS-C locus and that the histone H3 at the HIS-C locus is methylated. We propose that SU(VAR)3-9 is involved in packaging HIS-C into a distinct chromatin domain that has some of the characteristics of ß-heterochromatin. We suggest that methylation of histone H3 is important for the chromatin structure at HIS-C. The chromosomal deficiency for the HIS-C is also a suppressor of PEV. In contrast to what might be expected, we show that hemizygosity for the HIS-C locus leads to a substantial increase in the histone transcripts.

This article has been cited by other articles:

				R. B. Beckstead, S. S. Ner, K. G. Hales, T. A. Grigliatti, B. S. Baker, and H. J. Bellen Bonus, a Drosophila TIF1 Homolog, Is a Chromatin-Associated Protein That Acts as a Modifier of Position-Effect Variegation Genetics, February 1, 2005; 169(2): 783 - 794. [Abstract] [Full Text] [PDF]