Aid from repeat-binding and architectural maintenance proteins important in D. melanogaster dosage compensation
Authors: Maggie Sneideman; Victoria Meller
Affiliation: Wayne State University
Keywords: i. dosage compensation; s. siRNA/RNAi
Drosophila melanogaster males carry one X and one Y chromosome, but females have two X chromosomes. To equalize the amount of expression of the X-linked genes between the sexes, males increase the expression of X-linked genes approximately two-fold. This is mediated by the Male-Specific Lethal (MSL) complex, which modifies chromatin to elevate expression. The MSL complex first binds at Chromatin Entry Sites (CES) on the X, and then spreads into nearby active genes. CES contain a short motif that is bound by the adapter protein CLAMP. CLAMP is necessary to attract the MSL complex to the CES. However, these motifs are also found on the autosomes. These autosomal motifs also bind CLAMP, but fail to recruit the MSL complex. Another factor must therefore distinguish the X from the autosomes. The X chromosome is strikingly enriched for chromosome-specific repeats. One of these is the 1.688X repeats. Our lab has previously shown that the 1.688X repeats play a role in identifying the X. The focus of my project is to identify non-histone proteins that could participate in X identification by binding to 1.688X repeats. We selected known satellite DNA binding proteins, proteins with X-specific or male-specific effects, proteins with AT hook motifs, and heterochromatin factors. I will use knock down lines of my candidate genes to test for a male specific phenotype. I will mate these lines to a dosage compensation compromised line to determine if it genetically interacts with the CES. To determine if these proteins localize to the 1.688X repeats, ChIP for several candidates suspected to bind in this repeat region will be performed. Lastly, I will use Reem Makki’s dual luciferase reporter assay to identify candidate genes necessary for recruitment of compensation by the 1.688X repeats or CES. Thus far, ISWI, D1, and SAF-A appear to have a genetic interaction with the CES.