The RNA helicase DDX53 (CAGE) contributes to RNA metabolism in a human germ cell model

Abstract DDX53 (DEAD-box helicase 53, known also as CAGE) is an intronless gene on the X chromosome, which expression shows strong testis specificity. It belongs to the group of cancer-testis (CT) antigens, with most studies to date focusing on its role in cancer, but the precise biological function of DDX53 remains unclear. Previous reports identifying rare DDX53 variants in infertile men provided the rationale for investigating the role of DDX53 in the context of human spermatogenesis. By using the human seminoma cell line (TCam-2) as an in vitro male germline model, we aimed to investigate the function and molecular targets of DDX53 protein. Our eCLIP and RNA-seq data show that DDX53 protein directly interacts with numerous RNA molecules, drives transcriptome changes in human cells, and is involved in alternative splicing of RNA. Moreover, we identified potential DDX53 protein interactors using Co-IP-MS approach. Subcellular localization analysis by confocal microscopy indicated a predominantly cytoplasmic distribution of DDX53, with partial nuclear presence in TCam-2 cells. We also identified DDX53-positive structures that may correspond to germ granule-like assemblies, although their precise nature remains to be determined. Additionally, we confirmed DDX53 presence in human testis using a specific, commercially available anti-DDX53 antibody. Our data indicate that DDX53 protein acts as a regulator of RNA metabolism in human cells. Collectively, we show that DDX53 participates in transcriptome regulation (including splicing) in male germ cells and exhibits transcriptomewide RNA interactions, but its wider biological role remains to be clarified.