The p16INK4a protein regulates cell cycle progression mainly by inhibiting the activity of G1-phase cyclin-dependent kinases (CDKs) 4 and 6, the subsequent retinoblastoma protein (pRb) phosphorylation and E2F transcription factor release. The p16INK4a protein can also repress the activity of other transcription factors, such as c-myc, nuclear factorkappaB and c-Jun/AP1. Here, we report that, in two p16WT and p53 WT cell lines (MCF7 and U87), p16INK4a overexpression induces a dramatic decrease in CDK1 protein expression. In response to p16 INK4a, the decreased rate of CDK1 protein synthesis, its unchanged protein half-life, unreduced CDK1 mRNA steady-state levels and mRNA half-life allow us to hypothesize that p16INK4a could regulate CDK1 expression at the post-transcriptional level. This CDK1 downregulation is mediated by the 3 0 -untranslated region (3 0 UTR) of CDK1 mRNA as shown by translational inhibition in luciferase assays and is associated with a modified expression balance of microRNAs (miRNAs) that potentially regulate CDK1, analyzed by TaqMan Human microRNA Array. The p16 INK4a-induced expression of two miRNAs (miR-410 and miR-650 chosen as an example) in MCF7 cells is confirmed by individual reverse transcriptionqPCR. Furthermore, we show the interaction of miR-410 or miR-650 with CDK1-3 0 UTR by luciferase assays. Endogenous CDK1 expression decreases upon both miRNA overexpression and increases with their simultaneous inhibition. The induction of miR-410, but not miR-650 could be related to the pRb/E2F pathway. These results demonstrate the post-transcriptional inhibition of CDK1 by p16 INK4a . We suggest that p16INK4a may regulate gene expression by modifying the functional equilibrium of transcription factors and consequently the expression balance of miRNAs.