Chromatin reader component of the transcription regulatory histone acetylation (HAT) complex SAGA. Sgf29 specifically recognizes and binds methylated 'Lys-4' of histone H3 (H3K4me), with a preference for trimethylated form (H3K4me3). In the SAGA complex, sgf29 is required to facilitate crosstalk between gcn5 acetyltransferase activity and H3K4me3 recognition. At the promoters, SAGA is required for recruitment of the basal transcription machinery. It influences RNA polymerase II transcriptional activity through different activities such as TBP interaction and promoter selectivity, interaction with transcription activators, and chromatin modification through histone acetylation and deubiquitination. SAGA acetylates nucleosomal histone H3 to some extent (to form H3K9ac, H3K14ac, H3K18ac and H3K23ac)