Proteolysis of Xenopus Cip-type CDK inhibitor, p16Xic2, is regulated by PCNA binding and CDK2 phosphorylation

Xi Ning Zhu, Dong Hyun Kim, Horng Ru Lin, Varija N. Budhavarapu, Herbert B. Rosenbaum, Paul R. Mueller, Patricia R Yew

Research output: Contribution to journalArticle

Abstract

Background: Cell division is positively regulated by cyclin-dependent kinases (CDKs) partnered with cyclins and negatively regulated by CDK inhibitors. In the frog, Xenopus laevis, three types of CDK inhibitors have been described: p27Xic1 (Xic1) which shares sequence homology with both p21Cip1 and p27Kip1 from mammals, p16Xic2 (Xic2) which shares sequence homology with p21Cip1, and p17Xic3 (Xic3) which shares sequence homology with p27Kip1. While past studies have demonstrated that during DNA polymerase switching, Xic1 is targeted for protein turnover dependent upon DNA, Proliferating Cell Nuclear Antigen (PCNA), and the ubiquitin ligase CRL4Cdt2, little is known about the processes that regulate Xic2 or Xic3.Methods: We used the Xenopus interphase egg extract as a model system to examine the regulation of Xic2 by proteolysis and phosphorylation.Results: Our studies indicated that following primer synthesis during the initiation of DNA replication, Xic2 is targeted for DNA- and PCNA-dependent ubiquitin-mediated proteolysis and that Cdt2 can promote Xic2 turnover. Additionally, during interphase, Xic2 is phosphorylated by CDK2 at Ser-98 and Ser-131 in a DNA-independent manner, inhibiting Xic2 turnover. In the presence of double-stranded DNA ends, Xic2 is also phosphorylated at Ser-78 and Ser-81 by a caffeine-sensitive kinase, but this phosphorylation does not alter Xic2 turnover. Conversely, in the presence or absence of DNA, Xic3 was stable in the Xenopus interphase egg extract and did not exhibit a shift indicative of phosphorylation.Conclusions: During interphase, Xic2 is targeted for DNA- and PCNA-dependent proteolysis that is negatively regulated by CDK2 phosphorylation. During a response to DNA damage, Xic2 may be alternatively regulated by phosphorylation by a caffeine-sensitive kinase. Our studies suggest that the three types of Xenopus CDK inhibitors, Xic1, Xic2, and Xic3 appear to be uniquely regulated which may reflect their specialized roles during cell division or early development in the frog.

Original languageEnglish (US)
Article number5
JournalCell Division
Volume8
Issue number1
DOIs
StatePublished - Apr 22 2013

Fingerprint

Proteolysis
Phosphorylation
Cyclin-Dependent Kinases
Proliferating Cell Nuclear Antigen
Xenopus
Interphase
DNA
Sequence Homology
Ubiquitin
Caffeine
Anura
Cell Division
Ovum
Phosphotransferases
Cyclins
Cells
Xenopus laevis
DNA-Directed DNA Polymerase
Ligases
DNA Replication

Keywords

  • CDK inhibitor
  • PCNA
  • Phosphorylation
  • Proteolysis
  • Xenopus
  • Xic2

ASJC Scopus subject areas

  • Cell Biology
  • Biochemistry
  • Molecular Biology

Cite this

Proteolysis of Xenopus Cip-type CDK inhibitor, p16Xic2, is regulated by PCNA binding and CDK2 phosphorylation. / Zhu, Xi Ning; Kim, Dong Hyun; Lin, Horng Ru; Budhavarapu, Varija N.; Rosenbaum, Herbert B.; Mueller, Paul R.; Yew, Patricia R.

In: Cell Division, Vol. 8, No. 1, 5, 22.04.2013.

Research output: Contribution to journalArticle

Zhu, Xi Ning ; Kim, Dong Hyun ; Lin, Horng Ru ; Budhavarapu, Varija N. ; Rosenbaum, Herbert B. ; Mueller, Paul R. ; Yew, Patricia R. / Proteolysis of Xenopus Cip-type CDK inhibitor, p16Xic2, is regulated by PCNA binding and CDK2 phosphorylation. In: Cell Division. 2013 ; Vol. 8, No. 1.
@article{ececec09dd634895ad92ed03c6987d0c,
title = "Proteolysis of Xenopus Cip-type CDK inhibitor, p16Xic2, is regulated by PCNA binding and CDK2 phosphorylation",
abstract = "Background: Cell division is positively regulated by cyclin-dependent kinases (CDKs) partnered with cyclins and negatively regulated by CDK inhibitors. In the frog, Xenopus laevis, three types of CDK inhibitors have been described: p27Xic1 (Xic1) which shares sequence homology with both p21Cip1 and p27Kip1 from mammals, p16Xic2 (Xic2) which shares sequence homology with p21Cip1, and p17Xic3 (Xic3) which shares sequence homology with p27Kip1. While past studies have demonstrated that during DNA polymerase switching, Xic1 is targeted for protein turnover dependent upon DNA, Proliferating Cell Nuclear Antigen (PCNA), and the ubiquitin ligase CRL4Cdt2, little is known about the processes that regulate Xic2 or Xic3.Methods: We used the Xenopus interphase egg extract as a model system to examine the regulation of Xic2 by proteolysis and phosphorylation.Results: Our studies indicated that following primer synthesis during the initiation of DNA replication, Xic2 is targeted for DNA- and PCNA-dependent ubiquitin-mediated proteolysis and that Cdt2 can promote Xic2 turnover. Additionally, during interphase, Xic2 is phosphorylated by CDK2 at Ser-98 and Ser-131 in a DNA-independent manner, inhibiting Xic2 turnover. In the presence of double-stranded DNA ends, Xic2 is also phosphorylated at Ser-78 and Ser-81 by a caffeine-sensitive kinase, but this phosphorylation does not alter Xic2 turnover. Conversely, in the presence or absence of DNA, Xic3 was stable in the Xenopus interphase egg extract and did not exhibit a shift indicative of phosphorylation.Conclusions: During interphase, Xic2 is targeted for DNA- and PCNA-dependent proteolysis that is negatively regulated by CDK2 phosphorylation. During a response to DNA damage, Xic2 may be alternatively regulated by phosphorylation by a caffeine-sensitive kinase. Our studies suggest that the three types of Xenopus CDK inhibitors, Xic1, Xic2, and Xic3 appear to be uniquely regulated which may reflect their specialized roles during cell division or early development in the frog.",
keywords = "CDK inhibitor, PCNA, Phosphorylation, Proteolysis, Xenopus, Xic2",
author = "Zhu, {Xi Ning} and Kim, {Dong Hyun} and Lin, {Horng Ru} and Budhavarapu, {Varija N.} and Rosenbaum, {Herbert B.} and Mueller, {Paul R.} and Yew, {Patricia R}",
year = "2013",
month = "4",
day = "22",
doi = "10.1186/1747-1028-8-5",
language = "English (US)",
volume = "8",
journal = "Cell Division",
issn = "1747-1028",
publisher = "BioMed Central",
number = "1",

}

TY - JOUR

T1 - Proteolysis of Xenopus Cip-type CDK inhibitor, p16Xic2, is regulated by PCNA binding and CDK2 phosphorylation

AU - Zhu, Xi Ning

AU - Kim, Dong Hyun

AU - Lin, Horng Ru

AU - Budhavarapu, Varija N.

AU - Rosenbaum, Herbert B.

AU - Mueller, Paul R.

AU - Yew, Patricia R

PY - 2013/4/22

Y1 - 2013/4/22

N2 - Background: Cell division is positively regulated by cyclin-dependent kinases (CDKs) partnered with cyclins and negatively regulated by CDK inhibitors. In the frog, Xenopus laevis, three types of CDK inhibitors have been described: p27Xic1 (Xic1) which shares sequence homology with both p21Cip1 and p27Kip1 from mammals, p16Xic2 (Xic2) which shares sequence homology with p21Cip1, and p17Xic3 (Xic3) which shares sequence homology with p27Kip1. While past studies have demonstrated that during DNA polymerase switching, Xic1 is targeted for protein turnover dependent upon DNA, Proliferating Cell Nuclear Antigen (PCNA), and the ubiquitin ligase CRL4Cdt2, little is known about the processes that regulate Xic2 or Xic3.Methods: We used the Xenopus interphase egg extract as a model system to examine the regulation of Xic2 by proteolysis and phosphorylation.Results: Our studies indicated that following primer synthesis during the initiation of DNA replication, Xic2 is targeted for DNA- and PCNA-dependent ubiquitin-mediated proteolysis and that Cdt2 can promote Xic2 turnover. Additionally, during interphase, Xic2 is phosphorylated by CDK2 at Ser-98 and Ser-131 in a DNA-independent manner, inhibiting Xic2 turnover. In the presence of double-stranded DNA ends, Xic2 is also phosphorylated at Ser-78 and Ser-81 by a caffeine-sensitive kinase, but this phosphorylation does not alter Xic2 turnover. Conversely, in the presence or absence of DNA, Xic3 was stable in the Xenopus interphase egg extract and did not exhibit a shift indicative of phosphorylation.Conclusions: During interphase, Xic2 is targeted for DNA- and PCNA-dependent proteolysis that is negatively regulated by CDK2 phosphorylation. During a response to DNA damage, Xic2 may be alternatively regulated by phosphorylation by a caffeine-sensitive kinase. Our studies suggest that the three types of Xenopus CDK inhibitors, Xic1, Xic2, and Xic3 appear to be uniquely regulated which may reflect their specialized roles during cell division or early development in the frog.

AB - Background: Cell division is positively regulated by cyclin-dependent kinases (CDKs) partnered with cyclins and negatively regulated by CDK inhibitors. In the frog, Xenopus laevis, three types of CDK inhibitors have been described: p27Xic1 (Xic1) which shares sequence homology with both p21Cip1 and p27Kip1 from mammals, p16Xic2 (Xic2) which shares sequence homology with p21Cip1, and p17Xic3 (Xic3) which shares sequence homology with p27Kip1. While past studies have demonstrated that during DNA polymerase switching, Xic1 is targeted for protein turnover dependent upon DNA, Proliferating Cell Nuclear Antigen (PCNA), and the ubiquitin ligase CRL4Cdt2, little is known about the processes that regulate Xic2 or Xic3.Methods: We used the Xenopus interphase egg extract as a model system to examine the regulation of Xic2 by proteolysis and phosphorylation.Results: Our studies indicated that following primer synthesis during the initiation of DNA replication, Xic2 is targeted for DNA- and PCNA-dependent ubiquitin-mediated proteolysis and that Cdt2 can promote Xic2 turnover. Additionally, during interphase, Xic2 is phosphorylated by CDK2 at Ser-98 and Ser-131 in a DNA-independent manner, inhibiting Xic2 turnover. In the presence of double-stranded DNA ends, Xic2 is also phosphorylated at Ser-78 and Ser-81 by a caffeine-sensitive kinase, but this phosphorylation does not alter Xic2 turnover. Conversely, in the presence or absence of DNA, Xic3 was stable in the Xenopus interphase egg extract and did not exhibit a shift indicative of phosphorylation.Conclusions: During interphase, Xic2 is targeted for DNA- and PCNA-dependent proteolysis that is negatively regulated by CDK2 phosphorylation. During a response to DNA damage, Xic2 may be alternatively regulated by phosphorylation by a caffeine-sensitive kinase. Our studies suggest that the three types of Xenopus CDK inhibitors, Xic1, Xic2, and Xic3 appear to be uniquely regulated which may reflect their specialized roles during cell division or early development in the frog.

KW - CDK inhibitor

KW - PCNA

KW - Phosphorylation

KW - Proteolysis

KW - Xenopus

KW - Xic2

UR - http://www.scopus.com/inward/record.url?scp=84876740254&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84876740254&partnerID=8YFLogxK

U2 - 10.1186/1747-1028-8-5

DO - 10.1186/1747-1028-8-5

M3 - Article

C2 - 23607668

AN - SCOPUS:84876740254

VL - 8

JO - Cell Division

JF - Cell Division

SN - 1747-1028

IS - 1

M1 - 5

ER -