PMCCPMCCPMCC

Search tips
Search criteria 

Advanced

 
Logo of mbcLink to Publisher's site
 
Mol Biol Cell. 1992 July; 3(7): 805–818.
PMCID: PMC275636

Characterization of four B-type cyclin genes of the budding yeast Saccharomyces cerevisiae.

Abstract

The previously described CLB1 and CLB2 genes encode a closely related pair of B-type cyclins. Here we present the sequences of another related pair of B-type cyclin genes, which we term CLB3 and CLB4. Although CLB1 and CLB2 mRNAs rise in abundance at the time of nuclear division, CLB3 and CLB4 are turned on earlier, rising early in S phase and declining near the end of nuclear division. When all possible single and multiple deletion mutants were constructed, some multiple mutations were lethal, whereas all single mutants were viable. All lethal combinations included the clb2 deletion, whereas the clb1 clb3 clb4 triple mutant was viable, suggesting a key role for CLB2. The inviable multiple clb mutants appeared to have a defect in mitosis. Conditional clb mutants arrested as large budded cells with a G2 DNA content but without any mitotic spindle. Electron microscopy showed that the spindle pole bodies had duplicated but not separated, and no spindle had formed. This suggests that the Clb/Cdc28 kinase may have a relatively direct role in spindle formation. The two groups of Clbs may have distinct roles in spindle formation and elongation.

Full text

Full text is available as a scanned copy of the original print version. Get a printable copy (PDF file) of the complete article (3.8M), or click on a page image below to browse page by page.

Images in this article

Click on the image to see a larger version.

Articles from Molecular Biology of the Cell are provided here courtesy of American Society for Cell Biology