Cyclin-K is a
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
that in humans is encoded by the ''CCNK''
gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
.
Function
The protein encoded by this gene is a member of the transcription cyclin family. These cyclins may regulate
transcription through their association with and activation of
cyclin-dependent kinases (CDKs) through conformational changes.
Activation of CDKs through their cyclin partner, creates kinase complexes that will activate target proteins through
phosphorylation
In biochemistry, phosphorylation is described as the "transfer of a phosphate group" from a donor to an acceptor. A common phosphorylating agent (phosphate donor) is ATP and a common family of acceptor are alcohols:
:
This equation can be writ ...
. Targeted proteins can then ultimately regulate decisions of a cell's progression within the
cell cycle
The cell cycle, or cell-division cycle, is the sequential series of events that take place in a cell (biology), cell that causes it to divide into two daughter cells. These events include the growth of the cell, duplication of its DNA (DNA re ...
to occur. This gene product may be seen to play a dual role in both regulating CDK and
RNA polymerase II
RNA polymerase II (RNAP II and Pol II) is a Protein complex, multiprotein complex that Transcription (biology), transcribes DNA into precursors of messenger RNA (mRNA) and most small nuclear RNA (snRNA) and microRNA. It is one of the three RNA pol ...
(RNAP2) activities.
Cyclin K only uses RNA recruitment to activate transcription.
Interactions
Cyclin K has been shown to interact with multiple CDKs including
CDK9 and latest CDK12 and CDK13.
Roles include helping to phosphorylate C-terminal domains of subunits of RNAP2.
Cyclin K is most noted for its associated induction of processive elongation.
Also, identified with
G1 and
S phase cyclin activity, however functions are not deeply understood.
Cyclin K also interacts with HIV nef protein.
In the presence of overexpressed Nef protein, Cyclin k and CDK9 binding is induced, inhibiting the positive elongation factor of other CDK9 binding complexes, resulting in an inhibition of specific HIV-1 gene expression.
CDK 13 may also be characterized to interact with HIV mRNA splicing, alongside Nef, and the underexpression of Gag and Env related proteins.
Cyclin K is indispensable for Leukemia growth. SETD1A, is also known to bind Cyclin K through its FLOS domain.
The interaction is shown to be important to DNA damage response genes and for Leukemia proliferation.
References
Further reading
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External links
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