DPY-26 and MIX-1: An Investigation of Dosage Compensation and Chromosome Condensation in C.elegans (2008)

Undergraduate: Lindsay Dick

Faculty Advisor: Jason Lieb
Department: Biology

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Organisms in which females and males have a different number of X chromosomes must regulate X-chromosome expression so that the overall expression of X-linked genes is approximately equivalent in both sexes. C. elegans hermaphrodites (XX) accomplish this feat via the Dosage Compensation Complex (DCC) which halves the transcription levels of each X chromosome. Two members of this complex, DPY-26 and MIX-1, also have functions in more general chromosomal processes. MIX-1 is a member of the condensin complex, which binds to chromosomes during mitosis to aid in their segregation, while DPY-26 is a condensin homolog with a role in meiosis. We developed antibodies to both proteins through a process of cloning, expression, and the immunization of rabbits. The antibodies were affinity purified and verified through Western blotting, RNA interference, and immunofluorescence. With use of immunoprecipitation followed by quantitative PCR, initial results showed that both MIX-1 and DPY-26 enriched for a known dosage compensation binding site (rex-1). Using chromatin immunoprecipitation, followed by hybridization to whole-genome microarrays (ChIP-chip), we mapped the binding locations of MIX-1 and DPY-26. We observed strong peaks surrounded by broader regions of DCC binding on the X-chromosomes, supporting Dr. Sevinc Ercan’s suggestion of a recruitment-and-spreading mechanism. Current experiments center around separating the mitotic and meiotic binding signals from DCC signals.