Telomere-independent Rap1 is an IKK adaptor and regulates NF-kappaB-dependent gene expression.
We describe a genome-wide gain-of-function screen for regulators of NF-kappaB, and identify Rap1 (Trf2IP), as an essential modulator of NF-kappaB-mediated pathways. NF-kappaB is induced by ectopic expression of Rap1, whereas its activity is inhibited by Rap1 depletion. In addition to localizing on telomeres, mammalian Rap1 forms a complex with IKKs (IkappaB kinases), and is crucial for the ability of IKKs to be recruited to, and phosphorylate, the p65 subunit of NF-kappaB to make it transcriptionally competent. Rap1-mutant mice display defective NF-kappaB activation and are resistant to endotoxic shock. Furthermore, levels of Rap1 are positively regulated by NF-kappaB, and human breast cancers with NF-kappaB hyperactivity show elevated levels of cytoplasmic Rap1. Similar to inhibiting NF-kappaB, knockdown of Rap1 sensitizes breast cancer cells to apoptosis. These results identify the first cytoplasmic role of Rap1 and provide a mechanism through which it regulates an important signalling cascade in mammals, independent of its ability to regulate telomere function.
Teo
Hsiangling
H
Laboratory of NFkappaB Signaling, Proteos, Singapore 138673, Singapore.
Ghosh
Sourav
S
Luesch
Hendrik
H
Ghosh
Arkasubhra
A
Wong
Ee Tsin
ET
Malik
Najib
N
Orth
Anthony
A
de Jesus
Paul
P
Perry
Anthony S
AS
Oliver
Jeffrey D
JD
Tran
Nhan L
NL
Speiser
Lisa J
LJ
Wong
Marc
M
Saez
Enrique
E
Schultz
Peter
P
Chanda
Sumit K
SK
Verma
Inder M
IM
Tergaonkar
Vinay
V
D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000502:physiology; D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D002850:Chromatography, Gel; D006367:HeLa Cells; D006801:Humans; D051550:I-kappa B Kinase / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D053208:Kaplan-Meier Estimate; D051379:Mice; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000235:genetics / Q000502:physiology; D016133:Polymerase Chain Reaction; D011485:Protein Binding / Q000235:genetics / Q000502:physiology; D034741:RNA, Small Interfering; D000089804:Shelterin Complex; D034501:Telomere-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D046888:Tissue Array Analysis
D016328:NF-kappa B; D034741:RNA, Small Interfering; D000089804:Shelterin Complex; C440809:TERF2IP protein, human; D034501:Telomere-Binding Proteins; D051550:I-kappa B Kinase