Single-stranded DNA-binding protein that preferentially binds to the sterol regulatory element (SRE) sequence 5'-GTGCGGTG-3', and thereby mediates transcriptional repression (PubMed:2562787). Has a role as transactivator of the Myc promoter (By similarity). Binds single-stranded RNA in a sequence-specific manner (By similarity). {ECO:0000250|UniProtKB:P53996, ECO:0000250|UniProtKB:P62634, ECO:0000269|PubMed:2562787}. [Isoform 1]: Binds G-rich elements in target mRNA coding sequences (PubMed:28329689). Prevents G-quadruplex structure formation in vitro, suggesting a role in supporting translation by resolving stable structures on mRNAs (PubMed:28329689). . [Isoform 2]: Binds to RNA. . [Isoform 4]: Binds to RNA. . [Isoform 5]: Binds to RNA. . [Isoform 6]: Binds to RNA. . [Isoform 8]: Binds to RNA. . This is the function of CNBP (CCHC-type zinc finger nucleic acid binding protein, Ensembl gene identifier ENSG00000169714).