Table II.
Components and Regulators of the S. pombe SIN
| Protein | Structural features | Function |
|---|---|---|
| SIN scaffold | ||
| cdc11p | Leucine rich repeat | Scaffold subunit; interacts with sid4p,spg1p, sid2p, cdc13p and cdc16p |
| ppc89p | SPB protein | Interacts with sid4p |
| sid4p | SPB protein | Interacts with cdc11p, plo1p and dma1p |
| Players | ||
| spg1p | GTPase | Interacts with cdc11p and cdc7p; spg1p-GTP binds cdc7p which process downstream signaling |
| cdc16p | GAP | Regulates GTP hydrolysis of spg1p |
| byr4p | Scaffold protein | Regulates GTP hydrolysis of spg1p |
| cdc7p | Ser/Thr kinase | Binds to spg1p-GTP and process downstream signaling |
| sid1p | PAK-related kinase | Binds to cd14p and process SIN signaling downstream to cdc7p kinase |
| cdc14p | SIN component | Binds to sid1p and process SIN signaling downstream to cdc7p kinase |
| sid2p | AGC-kinase | Binds to mob1p and is recruited to medial region at the end of anaphase thus assumed to trigger ring contraction and septum formation |
| mob1p | MOB1/phocein family | Binds to mob1p and is recruited to medial region at the end of anaphase thus assumed to trigger ring contraction and septum formation |
| Regulators | ||
| dma1p | FHA-RING finger protein | Prevents septation in spindle assembly checkpoint-arrested cells; may regulate plo1p localization at the SPB |
| zfs1p | Zinc-finger RNA binding protein | Prevents septation in spindle assembly checkpoint-arrested cells; targets unknown |
| scw1p | RNA binding protein | Rescues sid2p mutant alleles indirectly; probably through stabilization of microtubules |
| par1p | Regulatory subunit of PP2A | Negative regulator of SIN pathway; targets unknown |
| fin1p | NIMA-related kinase | Regulates spindle formation, affinity of plo1 for the SPB and activity of SIN at old pole. |
| rad24p | 14-3-3 protein | Retains phosphorylated flp1p in cytoplasm |
| sce3p | A putative RNA-binding protein that is homologous to human eIF4B | Rescues mutations in cdc11p; targets unknown |
| dnt1p | Nucleolar protein | Interacts negatively with the SIN proteins; function unknown |
| flp1p/clp1p | Phosphoprotein phosphatase | Functions in cytokinesis checkpoint CDC14 homolog |
| etd1p | Possible GEF | Association of cdc7p and sid2p at the SPB; degradation could be linked to inactivation of SIN |