__NOTOC__ Cleavage factors are two closely associated

protein complex A protein complex or multiprotein complex is a group of two or more associated polypeptide chains. Protein complexes are distinct from multienzyme complexes, in which multiple catalytic domains are found in a single polypeptide chain. Protein ...

es involved in the cleavage of the

3' untranslated region In molecular genetics, the three prime untranslated region (3′-UTR) is the section of messenger RNA (mRNA) that immediately follows the translation termination codon. The 3′-UTR often contains regulatory regions that post-transcriptionally ...

of a newly synthesized pre- messenger RNA (mRNA) molecule in the process of

gene transcription Transcription is the process of copying a segment of DNA into RNA. The segments of DNA transcribed into RNA molecules that can encode proteins are said to produce messenger RNA (mRNA). Other segments of DNA are copied into RNA molecules calle ...

. The cleavage is the first step in adding a

polyadenine tail Polyadenylation is the addition of a poly(A) tail to an RNA transcript, typically a messenger RNA (mRNA). The poly(A) tail consists of multiple adenosine monophosphates; in other words, it is a stretch of RNA that has only adenine bases. In euka ...

to the pre-mRNA, which is one of the necessary

post-transcriptional modification Transcriptional modification or co-transcriptional modification is a set of biological processes common to most eukaryotic cells by which an RNA primary transcript is chemically altered following transcription from a gene to produce a mature, f ...

s necessary for producing a mature mRNA molecule. In mammals the two cleavage factors are known as CFIm and CFIIm. The proteins that constitute these complexes are recruited to the cleavage site by

cleavage and polyadenylation specificity factor Cleavage and polyadenylation specificity factor (CPSF) is involved in the cleavage of the 3' signaling region from a newly synthesized pre- messenger RNA (pre-mRNA) molecule in the process of gene transcription. It is the first protein to bind ...

and

cleavage stimulatory factor Cleavage stimulatory factor or cleavage stimulation factor (CstF or CStF) is a heterotrimeric protein, made up of the proteins CSTF1 (55 kDa), CSTF2 (64kDa) and CSTF3 (77kDa), totalling about 200 kDa. It is involved in the cleavage of the 3' si ...

, and form a larger complex that also includes polyadenine polymerase (PAP), which performs the polyadenylation reaction.

The CFIm complex

Involved in the earliest step for the formation of the active cleavage complex, the CFIm complex is formed by three proteins of 25, 59 and 68 kDa, respectively: *CFIm25 (or CPSF5/ NUDT21) *CFIm59 (or CPSF7) *CFIm68 (or CPSF6) CFIm25 and CFIm68 are sufficient for the activity of the complex, proving the expected redundancy of CFIm68 and CFIm59, which share great sequence similarity.

The CFIIm complex

The CFIIm complex is responsible for transcription termination and triggering the disassembly of the

elongation complex Elongation may refer to: * Elongation (astronomy) * Elongation (geometry) * Elongation (plasma physics) * Part of transcription of DNA into RNA of all types, including mRNA, tRNA, rRNA, etc. * Part of translation (biology) of mRNA into proteins * ...

. It is composed of only two proteins: * PCF11 * CLP1

The CFIm complex

The CFIIm complex

References

Further reading