Sex chromosome evolution: Life, death and repetitive DNA.

Sex chromosome evolution: Life, death and repetitive DNA. Fly (Austin). 2015 Mar 9;:0 Authors: Deshpande N, Meller VH Abstract Dimorphic sex chromosomes create problems. Males of many species, including Drosophila, are heterogametic, with dissimilar X and Y chromosomes. The essential process of dosage compensation modulates the expression of X-linked genes in one sex to maintain a constant ratio of X to autosomal expression. This involves the regulation of hundreds of dissimilar genes whose only shared property is chromosomal address. Drosophila males dosage compensate by up regulating X-linked genes two fold. This is achieved by the Male Specific Lethal (MSL) complex, which is recruited to genes on the X chromosome and modifies chromatin to increase expression. How the MSL complex is restricted to X-linked genes remains unknown. Recent studies of sex chromosome evolution have identified a central role for two types of repetitive elements in X recognition. Helitrons carrying sites that recruit the MSL complex have expanded across the X chromosome in at least one Drosophila species. (1) Our laboratory found that siRNA from an X-linked satellite repeat promotes X recognition by a yet unknown mechanism. (2) The recurring adoption of repetitive elements as X-identify elements suggests that the large and mysterious fraction of the genome called "junk" DNA is actually instrumental in the evolution of sex chromosomes. PMID: 25751570...
Source: Fly - Category: Biology Authors: Tags: Fly (Austin) Source Type: research