Introduction
An intricate network of cyclin-dependent kinases (CDKs) are organized in a pathway to ensure that each cell accurately replicates its DNA and segregate it equally between the two daughter cells. One CDK–the CDK7 complex–cannot be so easily classified. CDK7 is both a CDK-activating kinase (CAK), which phosphorylates cell-cycle CDKs within the activation segment (T-loop), and a component of the general transcription factor TFIIH, which phosphorylates the C-terminal domain (CTD) of the largest subunit of Pol II. A proposed mode of CDK7 inhibition is the phosphorylation of cyclin H by CDK7 itself or by another kinase.
Read more about this topic: CDK7 Pathway
Famous quotes containing the word introduction:
“Do you suppose I could buy back my introduction to you?”
—S.J. Perelman, U.S. screenwriter, Arthur Sheekman, Will Johnstone, and Norman Z. McLeod. Groucho Marx, Monkey Business, a wisecrack made to his fellow stowaway Chico Marx (1931)
“The role of the stepmother is the most difficult of all, because you can’t ever just be. You’re constantly being tested—by the children, the neighbors, your husband, the relatives, old friends who knew the children’s parents in their first marriage, and by yourself.”
—Anonymous Stepparent. Making It as a Stepparent, by Claire Berman, introduction (1980, repr. 1986)
“Such is oftenest the young man’s introduction to the forest, and the most original part of himself. He goes thither at first as a hunter and fisher, until at last, if he has the seeds of a better life in him, he distinguishes his proper objects, as a poet or naturalist it may be, and leaves the gun and fish-pole behind. The mass of men are still and always young in this respect.”
—Henry David Thoreau (1817–1862)