hnRNP UL1 plays an important role 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 of human cells. Upon investigating its function, we found that hnRNP UL1 stimulates ribosomal DNA (rDNA) gene transcription. Moreover, we observed that cells with hnRNP UL1 silencing exhibited increased sensitivity to DNA damage. We also showed that hnRNP UL1 interacts with γH2A.X, RPA32, XRCC1, and Chk1 in cell nucleoli, suggesting its involvement in the repair of rDNA damage.

7DRB1 (HYL1) is a double-stranded RNA binding protein involved in miRNA processing in plants. 8 It is a core component of the Microprocessor complex and enhances the efficiency and 9 precision of miRNA processing by DCL1 protein. In this work, we report a novel function of 10 DRB1 protein in the transcription of MIR genes. DRB1 co-localizes with RNA Polymerase II and 11 affects its distribution along MIR genes. Moreover, proteomic experiments revealed that 12 DRB1 protein interacts with many transcription factors. Finally, we show that the action of 13 DRB1 is not limited to MIR genes as it impacts expression of many other genes, majority of 14 which are involved in plant response to light. These discoveries add DRB1 as another player 15 of gene regulation at transcriptional level, independent of its role in miRNA biogenesis. 16