Breast Carcinoma-Amplified Sequence 2 (BCAS2) is a member of the SPF27 family. BCAS2 is a nuclear protein and widely expressed in many rtissues. BCAS2 is identified as being overexpressed in various breast cancer cell lines. BCAS2 is a component of the spliceosome, taking part in the removal of introns from mRNA precursors. BCAS2 interacts with estrogen receptor alpha and beta, thyroid hormone receptor beta, peroxisome proliferator-activated receptor gamma. BCAS2 functions as an ER co-activator and is capable of enhancing ER-mediated transcription.