Dicty News Electronic Edition Volume 25, number 4 August 12, 2005 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to dicty@northwestern.edu or by using the form at http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit. Back issues of Dicty-News, the Dicty Reference database and other useful information is available at dictyBase - http://dictybase.org. ============= Abstracts ============= A secreted factor represses cell proliferation in Dictyostelium Debra A. Brock and Richard H. Gomer Howard Hughes Medical Institute and Department of Biochemistry and Cell Biology, MS-140, Rice University, 6100 S. Main Street, Houston, TX 77005 Development, in press Many cells appear to secrete factors called chalones that limit their proliferation, but in most cases the factors have not been identified. We found that growing Dictyostelium cells secrete a 60 kDa protein called AprA for autocrine proliferation repressor. AprA has similarity to putative bacterial proteins of unknown function. Compared to wild-type cells, aprA null cells proliferate faster while AprA overexpressing cells proliferate slower. Growing wild-type cells secrete a factor that inhibits the proliferation of wild-type and aprAř cells; this activity is not secreted by aprAř cells. AprA purified by immunoprecipitation also slows the proliferation of wild-type and aprAř cells. Compared to wild-type, there is a higher percentage of multinucleate cells in the aprAř population, and when starved aprAř cells form abnormal structures that contain fewer spores. AprA may thus decrease the number of multinucleate cells and increase spore production. Together, the data suggest that AprA functions as part of a Dictyostelium chalone. Submitted by: Richard Gomer [richard@rice.edu>] ============================================================================== [End Dicty News, volume 25, number 4]