Send to

Choose Destination
RNA Biol. 2020 Jan 10:1-14. doi: 10.1080/15476286.2019.1709747. [Epub ahead of print]

Essential functions of the CNOT7/8 catalytic subunits of the CCR4-NOT complex in mRNA regulation and cell viability.

Author information

Cell Signal Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan.
Department of Biochemistry, Faculty of Pharmacy, Ain Shams University, Cairo, Egypt.
Department of Biochemistry and Metabolic Science, Graduate School of Medicine, Akita University, Akita, Japan.
Laboratory for Animal Resources and Genetic Engineering, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan.
Research Center for Medical Science, Jikei University School of Medicine, Tokyo, Japan.
Laboratory for Immunogenetics, Riken Center of Integrative Medical Sciences, Yokohama, Japan.


Shortening of mRNA poly(A) tails (deadenylation) to trigger their decay is mediated mainly by the CCR4-NOT deadenylase complex. While four catalytic subunits (CNOT6, 6L 7, and 8) have been identified in the mammalian CCR4-NOT complex, their individual biological roles are not fully understood. In this study, we addressed the contribution of CNOT7/8 to viability of primary mouse embryonic fibroblasts (MEFs). We found that MEFs lacking CNOT7/8 expression [Cnot7/8-double knockout (dKO) MEFs] undergo cell death, whereas MEFs lacking CNOT6/6L expression (Cnot6/6l-dKO MEFs) remain viable. Co-immunoprecipitation analyses showed that CNOT6/6L are also absent from the CCR4-NOT complex in Cnot7/8-dKO MEFs. In contrast, either CNOT7 or CNOT8 still interacts with other subunits in the CCR4-NOT complex in Cnot6/6l-dKO MEFs. Exogenous expression of a CNOT7 mutant lacking catalytic activity in Cnot7/8-dKO MEFs cannot recover cell viability, even though CNOT6/6L exists to some extent in the CCR4-NOT complex, confirming that CNOT7/8 is essential for viability. Bulk poly(A) tail analysis revealed that mRNAs with longer poly(A) tails are more numerous in Cnot7/8-dKO MEFs than in Cnot6/6l-dKO MEFs. Consistent with elongated poly(A) tails, more mRNAs are upregulated and stabilized in Cnot7/8-dKO MEFs than in Cnot6/6l-dKO MEFs. Importantly, Cnot6/6l-dKO mice are viable and grow normally to adulthood. Taken together, the CNOT7/8 catalytic subunits are essential for deadenylation, which is necessary to maintain cell viability, whereas CNOT6/6L are not.


CNOT6/6L; CNOT7/8; The CCR4-NOT complex; cell viability; deadenylation

Supplemental Content

Full text links

Icon for Taylor & Francis
Loading ...
Support Center