2007-02-01 17:08:03 · 3 answers · asked by Anonymous in Science & Mathematics ➔ Biology
Cyclin D is one part of a enzymatic complex which includes cdk4 or cdk2, cyclin D, and other accessory proteins. The main role of this complex in the cell cycle is getting the cell through the restriction point, also called 'start' in yeast. This point is the 'point of no return' to see if the cell has enough nutrients, etc to divide. Cyclin D/cdk2 or 4 is activated during restriction point and promotes S phase, which in turn promotes cyclin D degradation and assures the cell will continue through the cell cycle and not repeat S phase.
How does this complex work? Its a kinase complex, it phosphorylates Rb (and other things) which in turn activates E2F, which in turn drives expression of S phase genes.
This diagram helps.
http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mcb.figgrp.3557
Its discussed in more detail here: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Search&db=books&doptcmdl=GenBookHL&term=cyclin+d+AND+mcb%5Bbook%5D+AND+106238%5Buid%5D&rid=mcb.section.3553#3555
2007-02-02 11:48:22 · answer #1 · answered by gibbie99 4 · 0⤊ 0⤋
Cyclin D is a nuclear protien which disappears from the nucleus in S phase. Among key cell cycle regulators, cyclin D1 has been implicated most strongly as a proto-oncogene in several human tumor types, including breast carcinomas.
2007-02-02 02:48:20 · answer #2 · answered by georgd58 2 · 1⤊ 0⤋
It regulates the cell cycle.
2007-02-02 01:31:00 · answer #3 · answered by Doctor J 7 · 0⤊ 1⤋