A HOMOLOG OF THE HUMAN REGULATOR OF MITOTIC SPINDLE ASSEMBLY PROTEIN (RMSA-1) IS PRESENT IN CRANE-FLY AND IS ASSOCIATED WITH MEIOTIC CHROMOSOMES

In a previous study, we have shown that a newly identified chromosomal protein, RMSA-1 (Regulator of Mitotic Spindle Assembly-1), identified and cloned using a human autoimmune serum, is essential for mitotic s pindle assembly; we proposed that RMSA-1 was a previously unknown phys iological substrate for cdc 2 kinase. In the present study, we show th at this protein is present in crane fly and is associated with the chr omosomes of spermatocytes. A 31 kDa molecule in extracts from crane-fl y nuclei, isolated from larvae, pupae and adults, reacts with affinity -purified anti-RMSA-1 autoantibody, shown by immunoblotting. The autoa ntibody reacts, as shown by immunofluorescence, with crane-fly spermat ocyte chromosomes in prophase through anaphase of both meiosis-1 and m eiosis-II but does not react with preprophase or telophase nuclei or w ith spermatid nuclei. In all meiotic stages, the crane-fly sex chromos omes stain more intensely than the autosomes. We conclude that, since RMSA-1 is present in insect and mammalian cells, it is conserved acros s a variety of animal species. Further, since RMSA-1 binds to chromoso mes in meiotic cells, it also may be essential for assembly of the mei otic spindle.