[
Development & Evolution Meeting,
2006]
The C. elegans dosage compensation complex (DCC) assembles on hermaphrodite X chromosomes to downregulate gene expression two-fold. This ensures equal amounts of X-linked gene products in XX hermaphrodites and XO males. The DCC is similar to the 13S condensin complex, which is essential for mitotic and meiotic chromosome segregation. The four known DCC subunits are homologous to four of the five condensin proteins. In search of the fifth DCC subunit, antibodies against the unique dosage compensation protein, DPY-27, were used to immunoprecipitate the DCC from embryonic extracts. In collaboration with Ian McLeod and John R. Yates III, MUD-PIT analyses of precipitated proteins identified a novel DCC subunit, the protein encoded by F29D11.2. PSI -BLAST identified F29D11.2 as the homolog of the condensin subunit CAP-G. Using RNAi, we confirmed that this protein plays a role in dosage compensation. F29D11.2 is required for localization of other DCC subunits, and it will only localizes to the X in the presence of all other subunits, indicating that the protein is an integral member of the worm DCC.
Interestingly, F29D11.2 appears to also interact with the worm mitotic condensin. Our preliminary results indicate that the protein is present in immunoprecipitated mitotic condensin complexes. The protein also appears to localize to germline nuclei. Furthermore, animals homozygous for a null mutation in F29D11.2 arrest during larval development with chromosome segregation defects, including chromatin bridges connecting interphase nuclei. These results suggest that F29D11.2 may function in both dosage compensation and mitotic and meiotic chromosome segregation.