CNOT7

CNOT7 Full Name

CCR4-NOT transcription complex, subunit 7

CNOT7 Introduction

CCR4-NOT transcription complex subunit 7 (CNOT7), also designated as CAF1 or Caf1a, is a catalytic deadenylase subunit of the CCR4-NOT complex that functions alongside CNOT8 (Caf1b) as part of the CAF1 deadenylase module. Encoded by the CNOT7 gene on chromosome 8p22, CNOT7 is a member of the DEDD nuclease superfamily with 3'-to-5' exoribonuclease activity. Together with the CCR4 deadenylases (CNOT6/CNOT6L), the CAF1 subunits form the dual catalytic core that endows the CCR4-NOT complex with its deadenylation activity, the key initiating step in both constitutive and regulated mRNA decay pathways.

Figure 1. Strcuture of Protein CNOT7.

Mechanism of mRNA Deadenylation and Translational Repression
CNOT7 catalyzes the progressive shortening of mRNA poly(A) tails from the 3' end, and interestingly, its activity is stimulated by poly(A)-binding protein (PABPC1) bound to the poly(A) tail, creating a mechanism whereby translationally active mRNAs are preferentially targeted for deadenylation. This property functionally couples mRNA translation status to decay rates. Beyond its catalytic role, CNOT7 also contributes to the translational repression function of the CCR4-NOT complex independently of its deadenylase activity, through recruitment of the DEAD-box RNA helicase DDX6 and the translational repressor 4E-T. CNOT7 is selectively recruited to miRNA targets via GW182/TNRC6 proteins, where it collaborates with CNOT6/CNOT6L to mediate miRNA-induced silencing. The balance between CNOT7 and CNOT8 expression varies across tissues, with functional differences between these paralogs contributing to the fine-tuning of gene expression programs.

Physiological Functions and Implications in Spermatogenesis and Cancer
CNOT7 has a particularly prominent role in spermatogenesis: male mice with targeted deletion of Cnot7 are infertile, exhibiting defects in the transition from spermatogonia to spermatocytes and impaired meiotic progression. This phenotype is attributed to the failure to degrade specific mRNAs required to be cleared during the spermatogenic program, highlighting the essential role of post-transcriptional regulation in germ cell development. In cancer, CNOT7 exhibits dual functionality: it can suppress tumorigenesis by destabilizing oncogenic transcripts, while in other contexts it may facilitate cancer progression by silencing tumor suppressor mRNAs. CNOT7 expression is dysregulated in breast cancer, colorectal cancer, and hepatocellular carcinoma, and CNOT7 has been identified as a negative prognostic marker in certain breast cancer subtypes, making it a potential biomarker and therapeutic target.

Alternate Names for CNOT7

CNOT7; CCR4-NOT transcription complex, subunit 7; CAF1; CCR4-NOT transcription complex subunit 7; BTG1 binding factor 1; CAF-1; BTG1-binding factor 1; CCR4-associated factor 1; carbon catabolite repressor protein (CCR4)-associative factor 1; hCAF-1;