Ribosome biogenesis factor. Involved in nucleolar processing of pre-18S ribosomal RNA. Part of the small subunit (SSU) processome, first precursor of the small eukaryotic ribosomal subunit. During the assembly of the SSU processome in the nucleolus, many ribosome biogenesis factors, an RNA chaperone and ribosomal proteins associate with the nascent pre-rRNA and work in concert to generate RNA folding, modifications, rearrangements and cleavage as well as targeted d Involved in SSU pre-rRNA processing at sites A', A0, 1 and 2b. Required for optimal pre-ribosomal RNA transcription by RNA polymerase (PubMed:17699751, PubMed:19732766, PubMed:34516797). May be a transcriptional regulator (PubMed:22916032). {ECO:0000269|PubMed:17699751, ECO:0000269|PubMed:19732766, ECO:0000269|PubMed:22916032, ECO:0000269|PubMed:34516797}. (Microbial infection) Acts as a positive regulator of HIVEP1 which specifically binds to the DNA sequence 5'-GGGACTTTCC-3' found in enhancer elements of numerous viral promoters such as those of HIV-1, SV40, or CMV. . This is the function of UTP4 (UTP4 small subunit processome component, Ensembl gene identifier ENSG00000141076).