peptidyl-prolyl cis-trans isomerase NIMA-interacting 4; parvulin-14; par14; hpar14; parvulin-17; par17; hpar17; peptidyl-prolyl cis-trans isomerase Pin4; PPIase Pin4; peptidyl-prolyl cis/trans isomerase EPVH; hEPVH; Rotamase Pin4 (PIN4)
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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
- phosphorylated
- isoform 1 phosphorylation occurs both in the nucleus & the cytoplasm
- isoform 1 phosphorylation at Ser-19 does not affect its PPIase activity but is required for nuclear localization, & 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 by SUMO2 & SUMO3
- isoform 1 is found in pre-ribosomal ribonucleoprotein (pre-rRNP) complexes (putative)
Structure
- the PPIase domain enhances mitochondrial targeting belongs to the ppiC/parvulin rotamase family, PIN4 subfamily
- contains 1 PpiC domain
Compartment
- isoform 1:
- nucleus, nucleolus, cytoplasm, cytoskeleton, spindle
- colocalizes in the nucleolus during interphase & on the spindle apparatus during mitosis with NPM1
- isoform 2:
- mitochondria. mitochondrial matrix
- imported in a time- & 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
Alternative promoter usage
- named isoforms=2
- the first 25 amino acids are sufficient for mitochondrial targeting
Expression
- ubiquitous
- isoform 2 is much more stable than isoform 1 (at protein level)
- isoform 1 & isoform 2 are expressed in kidney, liver, blood vessel, brain, mammary gland, skeletal muscle, small intestine & submandibularis
- isoform 1 transcripts are much more abundant than isoform 2 in all tissues examined