부산대학교 도서관

N6-methyladenosine (m6A) is the most abundant internal messenger RNA (mRNA) modification. It affects nearly every aspect of mRNA metabolism such as splicing, transport and decay. m6A is a dynamic modification: a "writer" complex is responsible for its installation, whereas two "eraser" enzymes can remove this modification. m6A regulates gene expression by attracting effector or "reader" proteins that bind to it. YTH domain-containing family (YTHDF) proteins are a group of three cytoplasmic proteins YTHDF1, YTHDF2 and YTHDF3; that bind to m6A through the C-terminal YTH-domain. Among these proteins, YTHDF2 is the best characterised and it recruits the CCR4-NOT complex to mediate transcripts degradation by de-adenylation. The role of YTHDF2 in regulating the metabolism of transcripts is of central importance in several developmental, physiological and disease contexts. In zebrafish, YTHDF2 is required for the clearance of maternal transcripts during maternal to zygotic transition (MZT). Although in mice YTHDF2 is essential for oocyte maturation, it is still unknown whether YTHDF2 also has a key function during MZT. In this thesis I show that YTHDF2 is also required during MZT in mice. Furthermore, while it has been proved in vitro that YTHDF2 is an m6A reader, it has not been demonstrated that the functions attributed to YTHDF2 in vivo are dependent on m6A-binding or whether YTHDF2 has m6A-independent functions. Here I demonstrate that YTHDF2 binding to m6A-RNA is essential for YTHDF2 functions in vivo. Crystallography studies and in vitro assays have showed that YTHDF proteins all bind to m6A through a conserved aromatic cage and with similar binding affinity. Additionally, the YTHDF readers have a common RNA-binding motif. Therefore, it is debated whether YTHDF proteins function redundantly or whether they evolved context-dependent specific functions. Here I show that the activity of the YTHDF proteins in vivo is context-dependent. In summary, the key regulative role of YTHDF2 in different physiological contexts is linked to its role as an m6A reader, and, while YTHDF2 and YTHDF1 are redundant in certain contexts, they have evolved tissue-specific functions.