Uncovering human DCP1 is essential for mRNA decapping process and paralog-specific functions in gene regulation
The decapping complex is crucial in regulating gene expression by removing the mRNA cap structure. While DCP2 serves as the catalytic subunit in this complex, DCP1 is recognized as its major activator. In humans, there exist two distinct paralogs of DCP1, DCP1a and DCP1b, which each form separate decapping complexes. However, the endogenous mRNA targets of these DCP1 paralogs are largely unknown. To address the role of human DCP1 paralogs, we generated multiple DCP1-knockout cell lines and evaluated the importance of human DCP1 in mRNA decapping. Surprisingly, our results revealed that human DCP1 is essential for decapping process. We also discovered that the EVH1 domain of DCP1 is indispensable for the decapping activity of DCP2, as it enhances the mRNA-binding affinity of DCP2.  Additionally, the knock-out of DCP1 paralogs led to the significant activation of several pathways associated with cancer and mRNA processing, as well as the downregulation of DCP1a in various cancer types. Moreover, the knock-out cell lines of the two paralogs also exhibited distinct metabolome profiles. Overall, our findings highlight the crucial role of human DCP1 in mRNA decapping and shed light on the distinct functions of its two paralogs. Overall design: HEK-293T wild-type, DCP1a, DCP1b, or DCP1a/b-null cells were plated on 15 cm dishes 24 hrs before harvesting as previously described (46). Total RNA was extracted using the RNeasy Mini Kit (Qiagen) and a library prepared using the TruSeq RNA Sample Prep Kit (Illumina). Three biological replicates were analyzed. RNA-Seq libraries were sequenced using the HiSeq 3000 sequencing system (Illumina).