FOXO1 binds to the TAU5 motif and inhibits constitutively active androgen receptor splice variants

Laura R. Bohrer, Ping Liu, Jian Zhong, Yunqian Pan, James Angstman, Lucas J. Brand, Scott M. Dehm, Haojie Huang

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

Background: Aberrant activation of the androgen receptor (AR) is a major factor highly relevant to castration-resistant progression of prostate cancer (PCa). FOXO1, a key downstream effector of PTEN, inhibits androgen-independent activation of the AR. However, the underlying mechanism remains elusive. Methods: The inhibitory effect of FOXO1 on full-length and constitutively active splice variants of the AR was examined by luciferase reporter assays and real-time reverse transcription polymerase chain reaction (RT-qPCR). In vitro protein binding assays and western blot analyses were used to determine the regions in FOXO1 and AR responsible for their interaction. Results: We found that a putative transcription repression domain in the NH2-terminus of FOXO1 is dispensable for FOXO1 inhibition of the AR. In vitro protein binding assays showed that FOXO1 binds to the transcription activation unit 5 (TAU5) motif in the AR NH2-terminal domain (NTD), a region required for recruitment of p160 activators including SRC-1. Ectopic expression of SRC-1 augmented transcriptional activity of some, but not all AR splice variants examined. Forced expression of FOXO1 blocked the effect of SRC-1 on AR variants' transcriptional activity by decreasing the binding of SRC-1 to the AR NTD. Ectopic expression of FOXO1 inhibited expression of endogenous genes activated primarily by alternatively spliced AR variants in human castration-resistant PCa 22Rv1 cells. Conclusions: FOXO1 binds to the TAU5 motif in the AR NTD and inhibits ligand-independent activation of AR splice variants, suggesting the PTEN/FOXO1 pathway as a potential therapeutic target for inhibition of aberrant AR activation and castration-resistant PCa growth.

Original languageEnglish (US)
Pages (from-to)1017-1027
Number of pages11
JournalProstate
Volume73
Issue number10
DOIs
StatePublished - Jul 2013

Fingerprint

Androgen Receptors
Transcriptional Activation
Castration
Prostatic Neoplasms
Protein Binding
Luciferases
Androgens
Reverse Transcription
Western Blotting

Keywords

  • androgen receptor
  • FOXO1
  • prostate cancer
  • PTEN

ASJC Scopus subject areas

  • Urology
  • Oncology

Cite this

FOXO1 binds to the TAU5 motif and inhibits constitutively active androgen receptor splice variants. / Bohrer, Laura R.; Liu, Ping; Zhong, Jian; Pan, Yunqian; Angstman, James; Brand, Lucas J.; Dehm, Scott M.; Huang, Haojie.

In: Prostate, Vol. 73, No. 10, 07.2013, p. 1017-1027.

Research output: Contribution to journalArticle

Bohrer, LR, Liu, P, Zhong, J, Pan, Y, Angstman, J, Brand, LJ, Dehm, SM & Huang, H 2013, 'FOXO1 binds to the TAU5 motif and inhibits constitutively active androgen receptor splice variants', Prostate, vol. 73, no. 10, pp. 1017-1027. https://doi.org/10.1002/pros.22649
Bohrer, Laura R. ; Liu, Ping ; Zhong, Jian ; Pan, Yunqian ; Angstman, James ; Brand, Lucas J. ; Dehm, Scott M. ; Huang, Haojie. / FOXO1 binds to the TAU5 motif and inhibits constitutively active androgen receptor splice variants. In: Prostate. 2013 ; Vol. 73, No. 10. pp. 1017-1027.
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AU - Bohrer, Laura R.

AU - Liu, Ping

AU - Zhong, Jian

AU - Pan, Yunqian

AU - Angstman, James

AU - Brand, Lucas J.

AU - Dehm, Scott M.

AU - Huang, Haojie

PY - 2013/7

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N2 - Background: Aberrant activation of the androgen receptor (AR) is a major factor highly relevant to castration-resistant progression of prostate cancer (PCa). FOXO1, a key downstream effector of PTEN, inhibits androgen-independent activation of the AR. However, the underlying mechanism remains elusive. Methods: The inhibitory effect of FOXO1 on full-length and constitutively active splice variants of the AR was examined by luciferase reporter assays and real-time reverse transcription polymerase chain reaction (RT-qPCR). In vitro protein binding assays and western blot analyses were used to determine the regions in FOXO1 and AR responsible for their interaction. Results: We found that a putative transcription repression domain in the NH2-terminus of FOXO1 is dispensable for FOXO1 inhibition of the AR. In vitro protein binding assays showed that FOXO1 binds to the transcription activation unit 5 (TAU5) motif in the AR NH2-terminal domain (NTD), a region required for recruitment of p160 activators including SRC-1. Ectopic expression of SRC-1 augmented transcriptional activity of some, but not all AR splice variants examined. Forced expression of FOXO1 blocked the effect of SRC-1 on AR variants' transcriptional activity by decreasing the binding of SRC-1 to the AR NTD. Ectopic expression of FOXO1 inhibited expression of endogenous genes activated primarily by alternatively spliced AR variants in human castration-resistant PCa 22Rv1 cells. Conclusions: FOXO1 binds to the TAU5 motif in the AR NTD and inhibits ligand-independent activation of AR splice variants, suggesting the PTEN/FOXO1 pathway as a potential therapeutic target for inhibition of aberrant AR activation and castration-resistant PCa growth.

AB - Background: Aberrant activation of the androgen receptor (AR) is a major factor highly relevant to castration-resistant progression of prostate cancer (PCa). FOXO1, a key downstream effector of PTEN, inhibits androgen-independent activation of the AR. However, the underlying mechanism remains elusive. Methods: The inhibitory effect of FOXO1 on full-length and constitutively active splice variants of the AR was examined by luciferase reporter assays and real-time reverse transcription polymerase chain reaction (RT-qPCR). In vitro protein binding assays and western blot analyses were used to determine the regions in FOXO1 and AR responsible for their interaction. Results: We found that a putative transcription repression domain in the NH2-terminus of FOXO1 is dispensable for FOXO1 inhibition of the AR. In vitro protein binding assays showed that FOXO1 binds to the transcription activation unit 5 (TAU5) motif in the AR NH2-terminal domain (NTD), a region required for recruitment of p160 activators including SRC-1. Ectopic expression of SRC-1 augmented transcriptional activity of some, but not all AR splice variants examined. Forced expression of FOXO1 blocked the effect of SRC-1 on AR variants' transcriptional activity by decreasing the binding of SRC-1 to the AR NTD. Ectopic expression of FOXO1 inhibited expression of endogenous genes activated primarily by alternatively spliced AR variants in human castration-resistant PCa 22Rv1 cells. Conclusions: FOXO1 binds to the TAU5 motif in the AR NTD and inhibits ligand-independent activation of AR splice variants, suggesting the PTEN/FOXO1 pathway as a potential therapeutic target for inhibition of aberrant AR activation and castration-resistant PCa growth.

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