mRNA cap regulation in mammalian cell function and fate

In this review we explore the regulation of mRNA cap formation and its impact on mammalian cells. The mRNA cap is a highly methylated modification of the 5′ end of RNA pol II-transcribed RNA. It protects RNA from degradation, recruits complexes involved in RNA processing, export and translation initiation, and marks cellular mRNA as “self” to avoid recognition by the innate immune system. The mRNA cap can be viewed as a unique mark which selects RNA pol II transcripts for specific processing and translation. Over recent years, examples of regulation of mRNA cap formation have emerged, induced by oncogenes, developmental pathways and during the cell cycle. These signalling pathways regulate the rate and extent of mRNA cap formation, resulting in changes in gene expression, cell physiology and cell function. •The mRNA cap is a methylated modification of the 5′ terminus of mRNA.•RNA processing and translation factors are recruited to the mRNA cap.•The mRNA cap protects transcripts from degradation and defines mRNA as “self”.•Formation of the mRNA cap is regulated by cellular signalling pathways.•mRNA cap regulation results in changes in gene expression and cell function.