Disappearance of a novel protein component of the 26S proteasome during Xenopus oocyte maturation

We have prepared polyclonal antibodies against Xenopus 20S proteasomes. The antibodies cross-react with several proteins that are common to 20S and 26 S proteasomes and with at least two proteins that are unique to 26S proteas omes. The antibodies were used to analyze changes in the components of prot easomes during oocyte maturation and early development of Xenopus laevis. A novel protein with a molecular weight of 48 kDa, p48, was clearly detected in immature oocytes, but was found at very low levels in mature oocytes an d ovulated eggs. p48 was reduced to low levels during oocyte maturation, af ter maturation-promoting factor was activated. The amount of p48 in eggs re mained low during early embryonic development, but increased again after th e midblastula transition. These results show that at least one component of 26S proteasomes changes during oocyte maturation and early development and suggest that alterations in proteasome function may be important for the r egulation of developmental events, such as the rapid cell cycles, of the ea rly embryo. (C) 1999 Academic Press.