Knockdown of CNOT3, a subunit of the CCR4-NOT deadenylase complex, sensitizes A549 human non-small cell lung cancer cells to senescence-inducing stimuli

Cellular senescence is an essentially irreversible cell cycle arrest associated with upregulated inflammatory responses that contribute to various pathological and physiological processes, including aging, cancer, and cancer prevention. However, the underlying mechanisms are not fully understood. Here, we show that the downregulation of CNOT3, a subunit of the CCR4-NOT complex that deadenylates mRNA poly(A) tails, promotes cellular senescence in subpopulation of A549 human non-small cell lung cancer cells. Previous work has shown that CNOT3 knockdown upregulates p21 (CDKN1A), a cyclin-dependent kinase inhibitor. Since p21 is one of the key regulators of cellular senescence, we hypothesized that CNOT3 downregulation might lead to cellular senescence. Indeed, CNOT3 knockdown upregulates several key cellular senescence hallmarks, including p53, senescence-associated β-galactosidase activity, and senescence-associated secretory phenotype in subpopulation of A549 cell culture. The senescent cell hallmarks were more prominent in the culture after additional treatment with BI 2536, a polo-like kinase 1 inhibitor. These results suggest that CNOT3 downregulation followed by BI 2536 treatment upregulates the hallmarks of cellular senescence in A549 cell culture.