Chromatin reader component of some histone acetyltransferase (HAT) SAGA-type complexes like the TFTC-HAT, ATAC or STAGA complexes (PubMed:19103755, PubMed:20850016, PubMed:21685874, PubMed:26421618, PubMed:26578293). SGF29 specifically recognizes and binds methylated 'Lys-4' of histone H3 (H3K4me), with a preference for trimethylated form (H3K4me3) (PubMed:20850016, PubMed:21685874, PubMed:26421618, PubMed:26578293). In the SAGA-type complexes, SGF29 is required to recruit complexes to H3K4me (PubMed:20850016). Involved in the response to endoplasmic reticulum (ER) stress by recruiting the SAGA complex to H3K4me, thereby promoting histone H3 acetylation and cell survival (PubMed:23894581). Also binds non-histone proteins that are methylated on Lys residues: specifically recognizes and binds CGAS monomethylated on 'Lys-506' (By similarity). {ECO:0000250|UniProtKB:Q9DA08, ECO:0000269|PubMed:19103755, ECO:0000269|PubMed:20850016, ECO:0000269|PubMed:21685874, ECO:0000269|PubMed:23894581, ECO:0000269|PubMed:26421618, ECO:0000269|PubMed:26578293}. This is the function of SGF29 (SAGA complex associated factor 29, ENSG00000176476).