Investigation of the role of CCDC84 in splicing process

In eukaryotes, production of mature mRNAs from pre-mRNA needs to remove introns and subsequent exons joining. This process which is called splicing is carried out by the spliceosome that includes small ribonucleoprotein complexes. Each snRNP consists of a small RNA and proteins called core proteins. Although it is known that more than 300 different proteins, including the core proteins of snRNP, are involved in the assembly of the spliceosome, the functions of these proteins and the exact mechanism of splicing are not known. The mutations of some of the genes encoding the proteins involved in the assembly of spliceosome, including the core subunits of snRNP, have been associated with diseases. There is limited information about the function of CCDC84, which was shown to be involved in the splicing process and associated with Microcephalic Primordial Dwarfism by our group. This thesis aimed to elucidate the function of CCDC84 through the identification of the proteins that interact with CCDC84 at in vivo and in vitro conditions with immunoblot and immunofluorescence approaches, showing the effect of its deficiency on Cajal body formation with immunofluorescence and analyzing the effect of CCDC84 deficiency on splicing by minigene and RT-PCR approaches. As a result, our data showed that CCDC84 interacts directly with SART3 through the RNA binding motifs of SART3, takes place in the early stages of tri-snRNP construction, while its deficiency does not change the structure and the number of Cajal bodies, impairs the splicing of some of the minor introns. Our data indicate that SART3, which plays a crucial role in the U2 and U12 type tri-snRNP assembly, is directed to the U12 type tri-snRNP assembly by CCDC84.