Human INCENP colocalizes with the Aurora-B/AIRK2 kinase on chromosomes andis overexpressed in tumour cells

The inner centromere protein (INCENP), which has previously been described in chicken, frog and mouse, is required for correct chromosome segregation and cytokinesis. We have identified the human INCENP gene by library screen ing and reverse transcription-polymerase chain reaction (RT-PCR) and locali zed it to chromosomal region 11q12. HsINCENP is a single-copy gene that con sists of 17 exons and covers 25 kb of genomic DNA. The gene is expressed at highest levels in the colon, testis and prostate, consistent with its like ly role in cell proliferation. HsINCENP encodes a highly basic protein of 9 15 amino acids that localizes to metaphase chromosomes and to the mitotic s pindle and equatorial cortex at anaphase. Recently we showed that INCENP is stockpiled in a complex with the Aurora-B/XAIRK2 kinase in Xenopus eggs. H ere we demonstrate that, consistent with such an interaction, the two prote ins colocalize on human metaphase chromosomes. Levels of Aurora-B are incre ased in several human cancers, and we show here that HsINCENP protein level s are also significantly increased in several colorectal cancer cell lines.