We will continue to investigate factors required to combine the parental genomes and initiate nuclear division after fertilization. Our work centers on a Drosophila gene,fs(1)Ya (Young arrest), which codes for a maternal protein that is required for these early embryonic events. The fs(1)Ya protein is a cell cycle-regulated component of the nuclear lamina (the structural layer of the nuclear envelope). fs(1)Ya protein is normally present in the nuclear envelopes of the apposed male and female pronuclei. Embryos of fs(1)Ya mutants arrest with apposed pronuclei that lack normal nuclear envelopes. We will examine the functions and domains of fs(1)Ya protein, and continue studies aimed at placing fs(1)Ya in the context of other gene products needed for early embryogenesis or nuclear envelope function. In a major part of our proposed studies we will use in vitro and in vivo assays to determine whether fs(1)Ya function is necessary for the formation of a stable nuclear envelope, whether fs(1)Ya protein binds to DNA, and whether it plays a role specific to embryogenesis. In addition, we will continue our experiments to define important functional motifs in fs(1)Ya protein by cross-species comparisons and site-directed mutagenesis. We will also move """"""""outward"""""""" from fs(1)Ya by identifying and studying proteins that interact with it in the nuclear envelope. We are currently doing a genetic screen for dominant suppressors of a leaky fs(1)Ya mutation. We will also employ molecular approaches to identify proteins with which fs(1)Ya interacts. Finally, we will examine the distribution of fs(1)Ya protein in the pronuclei of mutant embryos arrested in the earliest stages of embryogenesis. We will initiate studies of genes whose products are needed for the correct localization of fs(1)Ya protein during pronuclear formation, apposition or division.
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