Plays a role in angiogenesis. Participates in the regulation of cell polarity and directional endothelial cell migration by mediating both the activation and recruitment of CDC42 and the reorganization of the actin cytoskeleton at the cell leading edge. Promotes filipodia formation (By similarity). Functions synergistically with PELP1 as a transcriptional coactivator of estrogen receptor-responsive genes. Stimulates histone acetyltransferase activity. Binds to chromatin. Plays a regulatory role in autophagic activity. In complex with PHAF1, associates with the preautophagosomal structure during both non-selective and selective autophagy (PubMed:33499712). Probably binds phosphatidylinositol 3-phosphate (PtdIns3P) which would mediate the recruitment preautophagosomal structures (PubMed:33499712). Interacts with histone H3, ESR1, KAT2B and PELP1; the interactions occur in a estrogen-dependent manner. Interacts with beta-tubulin and VIM. Interacts (via C-terminal) with PHAF1; the interaction is requrired for the association with the phagophore (PubMed:33499712). Localizes in the cytoplasm in stationary cells. Translocates from the cytoplasm to the leading edge in motile cells. Colocalizes with microtubules and intermediate filaments in both stationary and motile cells (By similarity). Associates with chromatin. Recruited to estrogen receptor-induced promoters in a PELP1-dependent manner. The BCAS3:PHAF1 complex is recruited to the preautophagosomal structures adjacent to the damaged mitochondria upon mitophagy in a PRKN-PINK1 dependent manner (PubMed:33499712). Expressed in stomach, liver, lung, kidney, prostate, testis, thyroid gland, adrenal gland, brain, heart, skeletal muscle, colon, spleen, small intestine, placenta, blood leukocyte and mammary epithelial cells. Expressed in undifferentiated ES cells. Expressed in blood islands and nascent blood vessels derived from differentiated ES cells into embryoid bodies (BD). Expressed in endothelial cells. Not detected in brain. Expressed in brain tumors (at protein level). Expressed in brain. Highly expressed in breast cancers and in glioma cell lines. Fetal. By estrogen. Has been proposed to contain 7 WD repeats. This prediction could not be reproduced. A chromosomal aberration involving BCAS3 has been found in some breast carcinoma cell lines. Translocation t(17;20)(q23;q13) with BCAS4. The disease is caused by variants affecting the gene represented in this entry. Belongs to the BCAS3 family. Truncated N-terminus. Truncated N-terminus.