PIN4

PIN4 is a member of the parvulin subfamily of the peptidyl-prolyl cis/trans isomerase protein family. The encoded protein catalyzes the isomerization of peptidylprolyl bonds, and may play a role in the cell cycle, chromatin remodeling, and/or ribosome biogenesis. The encoded protein may play an additional role in the mitochondria.

Full Name

Peptidylprolyl Cis/Trans Isomerase, NIMA-Interacting 4

Function

Isoform 1 is involved as a ribosomal RNA processing factor in ribosome biogenesis. Binds to tightly bent AT-rich stretches of double-stranded DNA.
Isoform 2 binds to double-stranded DNA.

Biological Process

rRNA processingIMP:UniProtKB

Cellular Location

Isoform 1
Nucleus, nucleolus
Cytoplasm, cytoskeleton, spindle
Cytoplasm
Colocalizes in the nucleolus during interphase and on the spindle apparatus during mitosis with NPM1.
Isoform 2
Mitochondrion
Mitochondrion matrix
Imported in a time- and membrane potential-dependent manner to the mitochondrial matrix, but without concomitant processing of the protein. Directed to mitochondria by a novel N-terminal domain that functions as non-cleavable mitochondrial targeting peptide.

PTM

Phosphorylated. Isoform 1 phosphorylation occurs both in the nucleus and the cytoplasm. Isoform 1 phosphorylation at Ser-19 does not affect its PPIase activity but is required for nuclear localization, and the dephosphorylation is a prerequisite for the binding to DNA. The unphosphorylated isoform 1 associates with the pre-rRNP complexes in the nucleus.
Isoform 2 is sumoylated with SUMO2 and SUMO3.