The novel role of hnRNP UL1 in rDNA transcription and rDNA repair in human cell nucleoli

hnRNP UL1 plays an important function in cell nuclei, where it is recruited to DNA damage sites and is involved in the repair of DNA double strand breaks. Furthermore, this protein is known as a transcriptional repressor of RNA polymerase II genes. In the present study, we have shown that hnRNP UL1 is also localized in the nucleoli. Revealing its function, we figured out that hnRNP UL1 stimulates rDNA gene transcription and may be involved in the transport of the proteins between the nucleolus and the nucleoplasm. Moreover, we observed that cells with hnRNP UL1 silencing are more sensitive to DNA damage, suggesting its role in rDNA repair pathways and nucleolar genome integrity. Indeed, we confirmed that hnRNP UL1 interacts with yH2A.X, RPA32, XRCC1, and Chk1 in cell nucleoli, suggesting its involvement in repairing of DNA damages.