The incenps: Chromosomal proteins with an essential cytoskeletal role during mitosis

Abstract

The INCENPs (INnerCENtromereProteins - Mr133 and 145 kDa) are tightly bound to chromatin until early metaphase, and arrive at the metaphase spindle plate as integral components of the chromosomes (Cooke et al., 1987; Earnshaw & Cooke, 1991). It is thus surprising that the INCENPs leave the chromosomes during the latter part of metaphase to become associated with fibrous structures traversing the metaphase plate (presumably the overlapping polar microtubules of the spindle). Following the onset of anaphase, the INCENPs remain closely associated with the stem body material in the central spindle and also become associated with the inner surface of the cell membrane at the position where the cleavage furrow subsequently forms.By combining library screening with reverse-transcriptase PCR, we have recovered cDNA clones that contain the complete open reading frames (ORFs) of the two chicken INCENPs. Class 1 INCENP cDNA contains an ORF of 839 codons, which includes a predicted central coiled-coil domain of about 200 residues.