Fin1p is a spindle pole body-related intermediate filament protein that forms cell cycle-specific filaments between spindle pole bodies in mother and daughter cells, and is able to self-assemble in vitro (1, 3).

FIN1 expression is induced during the S/G2 phase of the cell cycle (2), and Fin1p is a Clb5p-Cdc28p specific substrate that is fully phosphorylated immediately after its synthesis in early S phase. The protein is then dephosphorylated after degradation of Clb5p during mitosis (7). This Fin1p dephosphorylation is dependent on Bmh1p and Bmh2p, as the protein cannot be dephosphorylated in a bmh1 bmh2 double null mutant (2). Fin1p has higher affinity for Bmh2p than for Bmh1p (3), and Bmh2p only interacts with phosphorylated forms of Fin1p (2). Phosphorylated Fin1p also interacts with the Glc7p catalytic subunit of the protein phosphatase type 1 complex, suggesting that Glc7p and Bmh1p/Bmh2p are involved in regulating the phosphorylation state of Fin1p (2).

In resting cells Fin1p is undetectable, in small-budded cells Fin1p is localized in the nucleus, and during late mitosis Fin1p localizes to the spindle pole bodies (1). fin1 null mutants are viable on both minimal and rich growth media. Overexpression of FIN1 in haploid cells is lethal, and in diploid cells it results in very poor growth, altered cell morphology, and an accumulation of filamentous structures that resemble the neurofibrillary tangles found in cells of patients with Alzheimer's disease (1).

Last updated: 2005-10-07