Cyclin synthesis: Who needs it?

✍ Scribed by Jeremy Minshull

• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 818 KB
• Volume: 15
• Category: Article
• ISSN: 0265-9247
• DOI: 10.1002/bies.950150302

✦ Synopsis

leads to the appearance of a white spot in the centrc of the dark animal pole, a very convenient marker for first meiosis known as GVBD (Germinal Vesicle Breakdown, see Fig. 2).

Maturation Promoting Factor (MPF) was discovered in experiments cxamining thc mechanism by which progesterone causes oocyte maturation. MPF was the name given to an activity from progesterone-matured oocytes which could be microinjected into immature oocytes, causing them to mature without the need for direct progesterone stimulation' 21. These experiments suggested that progesterone normally causes the activation of MPF within the oocyte, and MPF in turn causes meiotic maturation. The subsequent discovery that almost all meiotic and mitotic cells contained MPF activity(3-6) led to the idea of a general inducer of Mphase, one that is conserved in eukaryotes from yeast to mammals.

The oocy tc maturation assay, although instrumental in the discovery of MPF, is neither quick nor easy, and only allowed MPF to be purified about 3O-T0ld(~). For their ultimately successful purification of MPF, Lohka ef al. developed a Xrnopus egg cell-free system to which they addcd sperm nuclei(x1. In this system, fractions were tested for MPF activity by their ability to induce chromosome condensation and nuclear envelope breakdown(". As well as freeing them from hours of manual oocyte defolliculation, the cell-free mitosis assay meant that Lohka et czl. purified the mitotic regulator they were looking for. and did not have to worry about what really goes on inside an oocyte during meiotic maturation.