Plays a structural role in chromatin. Chromatid cohesion molecule required for equal sister chromatid separation in anaphase. May form a stable link between chromatids in S phase that is split rather than removed in anaphase. Also required for spindle-kinetochore interaction in early mitosis and inhibit sister chromatid separation until the cleavage of Rad21 in anaphase. {ECO:0000269|PubMed:11882285}.