Functions as an E3-type small ubiquitin-like modifier (SUMO) ligase which sumoylates CHD3/Mi2-alpha, causing its release from DNA (PubMed:27068747). This results in suppression of CHD3/Mi2-alpha transcription repression, increased recruitment of RNA polymerase II to gene promoters and positive regulation of transcription including H1-5 and ribosomal proteins such as: RPS6, RPL10A, and RPL12 (PubMed:12663651, PubMed:17209048, PubMed:17220279, PubMed:27068747). The resulting increased transcriptional activity drives cell proliferation (PubMed:12663651, PubMed:17220279). Binds to 5'- TGTCG[CT]GA[CT]A-3' consensus sequences in gene promoters of ribosomal proteins (PubMed:12663651, PubMed:17209048, PubMed:17220279, PubMed:27068747). {ECO:0000269|PubMed:12663651, ECO:0000269|PubMed:17209048, ECO:0000269|PubMed:17220279, ECO:0000269|PubMed:27068747}. (Microbial infection) Binds to human adenovirus gene promoters and contributes to transcriptional repression and virus growth inhibition during early stages of infection. . This is the function of ZBED1 (zinc finger BED-type containing 1, ENSG00000214717).