Regulation of the oncogenic PIM1 kinase by SUMOylation
type: CreativeWork
description: PIM1 (Proviral Integration site for Murine leukemia virus site 1) is a constitutively active serine/threonine protein kinase that is induced physiologically by the JAK-STAT and NF-κB pathways. PIM1 mediates survival signalling in cells, and contributes to the development of resistance towards chemotherapy and radiotherapy. It is also overexpressed in a wide range of haematological malignancies, and in solid tumours of the prostate, colon, breast and lung among others, which makes it an attractive drug target. However, the mechanisms regulating PIM1 kinase activity and protein levels have remained largely unexplored. Based on PIM1 protein sequence analysis, I identified the presence of a conserved motif (IK169DE171) in the active site of PIM1 that is recognised by the Small ubiquitin-like modifier (SUMO). By site-directed mutagenesis of individual lysine residues in PIM1, I showed that PIM1 is covalently modified by SUMO at he consensus K169 site, and also at a second promiscuous site. However, the K169R mutant only abolished SUMOylation at one site, but the E171A mutant abolished SUMOylation at both sites. I also showed that members of the Protein inactivator of activated STATs (PIAS) family could act as E3 SUMO ligases for PIM1. SUMOylated PIM1 showed higher protein kinase activity in vitro when Histone H3.3 was used a substrate, indicating that SUMOylation might enhance PIM1 kinase activity. Interestingly, both K169R and E171A displayed substrate specificity in vitro and when expressed in cells, suggesting that SUMOylation might govern PIM1 substrate specificity under certain contexts. Cycloheximide chase analysis revealed that both K169R and K67M (catalytically inactive) mutants of PIM1 were less stable. This can be attributed to the observation that the K169R mutant is incapable of undergoing autophosphorylation similar to the K67M mutant of PIM1. This indicates that both K169 and K67 residues are critical for the intrinsic kinase activity, and may not represent…
abstract: PIM1 (Proviral Integration site for Murine leukemia virus site 1) is a constitutively active serine/threonine protein kinase that is induced physiologically by the JAK-STAT and NF-κB pathways. PIM1 mediates survival signalling in cells, and contributes to the development of resistance towards chemotherapy and radiotherapy. It is also overexpressed in a wide range of haematological malignancies, and in solid tumours of the prostate, colon, breast and lung among others, which makes it an attractive drug target. However, the mechanisms regulating PIM1 kinase activity and protein levels have remained largely unexplored. Based on PIM1 protein sequence analysis, I identified the presence of a conserved motif (IK169DE171) in the active site of PIM1 that is recognised by the Small ubiquitin-like modifier (SUMO). By site-directed mutagenesis of individual lysine residues in PIM1, I showed that PIM1 is covalently modified by SUMO at he consensus K169 site, and also at a second promiscuous site. However, the K169R mutant only abolished SUMOylation at one site, but the E171A mutant abolished SUMOylation at both sites. I also showed that members of the Protein inactivator of activated STATs (PIAS) family could act as E3 SUMO ligases for PIM1. SUMOylated PIM1 showed higher protein kinase activity in vitro when Histone H3.3 was used a substrate, indicating that SUMOylation might enhance PIM1 kinase activity. Interestingly, both K169R and E171A displayed substrate specificity in vitro and when expressed in cells, suggesting that SUMOylation might govern PIM1 substrate specificity under certain contexts. Cycloheximide chase analysis revealed that both K169R and K67M (catalytically inactive) mutants of PIM1 were less stable. This can be attributed to the observation that the K169R mutant is incapable of undergoing autophosphorylation similar to the K67M mutant of PIM1. This indicates that both K169 and K67 residues are critical for the intrinsic kinase activity, and may not represent…
author: Iyer, R. Sumanth
language: eng
date published: 2016
date modified: 2026-07-24T02:08:26Z
provider: University of Dundee
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Dundee