MCPIP3/Regnase-3 binds 14-3-3 proteins and contributes to the regulation of the cell cycle in human immortalized keratinocytes

Skin homeostasis is ensured by a fine-tuned balance of proliferation and differentiation of keratinocytes, disturbances in which may initiate or promote skin diseases. The monocyte chemotactic protein-induced protein 3 (MCPIP3), or Regnase-3, is a ribonuclease belonging to the MCPIP family. Keratinocyte-specific loss of MCPIP3 results in increased expression of genes related to cell division, accelerated epidermal proliferation rate, and abnormal differentiation. The aim of this study was to gain insights into the mechanisms by which MCPIP3 affects keratinocyte biology. Immunoprecipitation-proteomics was applied to identify putative interactors of MCPIP3 in HaCaT keratinocytes. It revealed that MCPIP3 forms complexes with keratin 14, 14-3-3 proteins and modulators of cell polarity. Silencing of MCPIP3 and keratin 14 led to significantly increased expression of S/G2 and G2/M phase markers, namely cyclin A2, cyclin B1 and histone H3 Ser10 phosphorylation. Simultaneous silencing of both genes had synergistic effect. Double thymidine block and release protocol was used to synchronize HaCaT cells and indicated that MCPIP3 reaches the highest level of expression in peri-mitotic cells. Altogether, our results uncover the significance of studying the post-transcriptional regulation of gene expression in the context of cell cycle related events, clarifying the mechanisms by which MCPIP3 modulates proliferation of keratinocytes.