Localization of residues in a novel DNA-binding domain of DmSNAP43 required for DmSNAPc DNA-binding activity

Transcription of snRNA genes depends upon the recognition of the proximal sequence element (PSE) by the snRNA activating protein complex SNAPc. In Drosophila melanogaster, all subunits of DmSNAPc (DmSNAP43, DmSNAP50, and DmSNAP190) are required for PSE-binding activity. Previous work demonstrated that a non-canonical DmSNAP43 domain bounded by residues 193–272 was essential for DmSNAPc to bind to the PSE. In this study, the contribution of amino acid residues within this domain to DNA binding by DmSNAPc was investigated by alanine-scanning mutagenesis. The results have identified two clusters of residues within this domain required for the sequence-specific DNA-binding activity of DmSNAPc.

► DmSNAP43 contacts snRNA gene promoters through a non-canonical DNA-binding domain.
► This domain contains three clusters of evolutionarily conserved amino acid residues.
► Alanine-scanning mutagenesis was carried out on all 70 non-alanine residues.
► Amino acids required for DmSNAPc DNA-binding activity were identified.
► Required residues localized to two of the three evolutionarily conserved clusters.