Cysteine-protease involved in male chromatin remodeling after fertilization co-localizes with α-tubulin at mitosis

We postulated an essential role for a cysteine‐protease in sea urchins sperm histones degradation which follows fertilization. We now report the purification of this enzyme, the determination of its N‐terminal amino acid sequence and the localization of the protein with antibodies generated against this amino‐terminal peptide. The immunofluorescence data confirmed the presence of this enzyme in the nucleus of unfertilized eggs. After fertilization labeling is observed both in female and male pronuclei suggesting a rapid recruitment of the enzyme to the male pronuclei. Interestingly, we have found that this cysteine‐protease persists in the nucleus of the zygotes during S phase of the cell cycle and co‐localizes with α‐tubulin that organizes the mitotic spindle during the initial embryonic cell division. © 2004 Wiley‐Liss, Inc.