Activator of S Phase Kinase

**Semantic type:** Amino Acid, Peptide, or Protein|Enzyme

**Definition:** Encoded by growth factor and E2F-regulated widely expressed human ASK Gene, 77-kD nuclear Activator of S Phase Kinase (dup) is a cyclin-like regulatory subunit of CDC7L1 kinase involved in G1/S transition. ASK mRNA and protein are low in G1, peak in S phase, and reduce in G2/M; ASK is extensively phosphorylated during S phase. Containing a bipartite NLS, conserved motifs N (N-terminus) and C (central region), and 2 PEST sequences, ASK appears essential for entry into S phase. Motif C is essential for CDC7L1 catalytic subunit interaction with ASK, a major activator of CDC7L1 kinase activity on MCM2.

**Synonyms:** - ASK - DBF4 Homolog - Dumbbell Former 4 Homolog