Mapping and characterization of the eukaryotic early pregnancy factor/chaperonin 10 gene family

Early pregnancy factor and mitochondrial chaperonin 10 have very different functions within mammals but the mature peptides have identical amino acid sequences. In order to understand the mechanisms by which identical proteins can have different functions and sites of activity, we have examined genomic DNA which could encode the protein. In most species studied, there is a large gene family of at least ten members with homology to the DNA sequence for this protein. Using a monochromosomal somatic cell hybrid panel, we have mapped the gene for human chaperonin 10 to chromosome 2. Other members of the human gene family map to several chromosomes. Chromosomes 1, 2 and 9 contain pseudogenes with Alu insertions while chromosome 16 has a pseudogene containing a short direct repeat flanking an insert. Chromosomes 1 and 16 may also carry a functional intronless copy of the EPF/Cpn10 sequence

Cyclin A/cdk2 coordinates centrosomal and nuclear mitotic events

Cyclin A/cdk2 has a role in progression through Sphase, and a large pool is also activated in G(2) phase. Here we report that this G(2) phase pool regulates the timing of progression into mitosis. Knock down of cyclin A by siRNA or addition of a specific cdk2 small molecule inhibitor delayed entry into mitosis by delaying cells in G(2) phase. The G(2) phase-delayed cells contained elevated levels of inactive cyclin B/cdk1. However, increased microtubule nucleation at the centrosomes was observed, and the centrosomes stained for markers of cyclin B/cdk1 activity. Both microtubule nucleation at the centrosomes and the phosphoprotein markers were lost with short-term treatment of the cdk1/2 inhibitor roscovitine but not the Mek1/2 inhibitor U0126. Cyclin A/cdk2 localized at the centrosomes in late G(2) phase after separation of the centrosomes but before the start of prophase. Thus G(2) phase cyclin A/cdk2 controls the timing of entry into mitosis by controlling the subsequent activation of cyclin B/cdk1, but also has an unexpected role in coordinating the activation of cyclin B/cdk1 at the centrosome and in the nucleus