Chromatin reader component of some histone acetyltransferase (HAT) SAGA-type complexes like the TFTC-HAT, ATAC or STAGA complexes. SGF29 specifically recognizes and binds methylated 'Lys-4' of histone H3 (H3K4me), with a preference for trimethylated form (H3K4me3). In the SAGA-type complexes, SGF29 is required to recruit complexes to H3K4me. Involved in the response to endoplasmic reticulum (ER) stress by recruiting the SAGA complex to H3K4me, thereby promoting histone H3 acetylation and cell survival. Interacts with dimethylated and trimethylated 'Lys-4' of histone H3 (H3K4me2 and H3K4me3), with a preference for the trimethylated form (H3K4me3). Component of some SAGA-type complexes. Component of the ADA2A-containing complex (ATAC), composed of KAT14, KAT2A, TADA2L, TADA3L, ZZ3, MBIP, WDR5, YEATS2, CCDC101 and DR1 (By similarity). Interacts with TADA3L, GCN5L2, SUPT3H and MYC (By similarity). The SGF29 C-terminal (also named tudor-like) domain mediates binding to methylated 'Lys-4' of histone H3 (H3K4me). Belongs to the SGF29 family.