Poly(A) RNA polymerase

Function

Poly(A) RNA polymerase protein Cid1 (Caffeine-Induced Death protein 1) is involved in cell cycle arrest where it inhibits unscheduled mitosis^[1]. Cid1 is found in fission yeast. Cid1 exists in 3 forms: apo I consists of 4 subunits; apo II consists of 2 subunits; UTP-bound form consists of 4 subunits.
Poly(A) RNA polymerase Gld2 is responsible for poly(A) tail lengthening. Gld2 activity in the brain is required for long-term memory^[2].

Structural highlights

The UTP binding site of Cid1 is between the N-terminal and C-terminal. The contains the (in magenta) in the N-terminal and the (in cyan) whose two conformations select between binding of UTP and ATP to Cid1 ^[3]. Water molecules are shown as red spheres.