Functional dissection of Mcm10: exploring the essential functions of a replication factor. Michael C. Reubens, Tim W. Christensen. Biology, East Carolina University, Greenville, NC.

   Life depends on a series of highly orchestrated and regulated biochemical processes collectively known as the cell cycle. It is through these heavily regulated stages that cells grow, divide, and accurately transmit their genetic material. The preservation of cellular identity and genomic stability through these stages requires that DNA replication take place with high fidelity, and that chromatin states are accurately passed from one generation to another to ensure the proper transcriptional state of the resulting cells. It has become more apparent that the processes of DNA replication and the establishment of epigenetic chromatin states are more intimately linked than once thought. A protein common to both processes, Mcm10, has become an interesting avenue of research in an attempt to better understand the dynamic link between these two processes. By utilizing an established collection of 29 independent Mcm10 mutant fly lines consisting of twenty two missense point mutations, four truncation alleles, two homozygous lethal alleles, and one hypomorphic allele we have begun to elucidate regions of this conserved protein that are either essential for, or dispensable for, given biological functions. Analysis of a hypomorphic allele demonstrates that reduced protein levels result in abnormal chromosome condensation phenotypes. Our truncation alleles have suggested that the only the N-terminal 388 amino acids of the protein are required for viability; however, the C-terminal 388 amino acids are required for female specific fertility, and the extreme C-terminal 65aa are required for proper endoreplication. The C-terminal 388 amino acids have been shown to contain a region important for the interaction with HP1 which overlaps with regions important for genomic stability, heterochromatin formation, and contains two independent homozygous lethal alleles. It is our hope that further analyses using this mutant collection will shed light on the essential nature of Mcm10 in Drosophila, and aid in a better understanding of replication, chromosome biology, and potentially oncogenesis.