The secrets of heterochromatin

Associated with the formation of centromeres and telomeres, heterochromatin is linked with the proper segregation of genetic material during cell division. Heterochromatin structure is also implicated in gene expression. Despite its importance in cellular genetic control, the formation of this material is poorly understood.

The 'Study of the determinants of heterochromatin formation and maintenance' (HETCHROMPROJECT) project has determined key molecular mechanisms that control heterochromatin formation. One major player is ARS-binding protein 1 (ABP1). The researchers used the yeast Schizosaccharomyces pombe, an ideal system, as many of its genetic control pathways have been preserved through evolution and appear in mammals.

The HETCHROMPROJECT researchers found that ABP1 can repress the transcription of small RNAs. Other genes were identified that have a role to play in switching small RNA transcription on and off. Specifically, small RNA is derepressed in the absence of clr3 histone deacetylase gene and the hip3 HIRA complex gene. These two genes code for products that are involved in gene silencing through regulation of the chromatin structure.

The next phase of research before completion of the project is to investigate the role of novel proteins involved in heterochromatin regulation. In preparation for this, the scientists have set up a two-step genetic screen. They identified 49 deletion strains that are ideal for studying alterations in heterochromatin structure in the centromere.

Heterochromatin is important for preserving chromosome segregation during cell division and maintaining genomic integrity. Project research promises to shed light on diseases caused by changes in heterochromatin that impair normal gene expression.