This domain is about 90 residues in length and is often found associated with the Pfam:PF02213 domain. The function of this domain is uncertain. It is possible that this domain is involved in DNA binding as it has three conserved positively charged residues, hence this domain has been named the plus-3 domain. It is found in yeast Rtf1 which may be a transcription elongation factor [1].

1: Synthetic lethal interactions suggest a role for the Saccharomyces cerevisiae Rtf1 protein in transcription elongation. Costa PJ, Arndt KM; Genetics 2000;156:535-547. PMID:11014804

2: Identification of RTF1, a novel gene important for TATA site selection by TATA box-binding protein in Saccharomyces cerevisiae. Stolinski LA, Eisenmann DM, Arndt KM; Mol Cell Biol 1997;17:4490-4500. PMID:9234706