A 55-kDa Protein (P55) of the Goat Uterus Mediates Nuclear Transport of the Estrogen-Receptor

Nirmala, P; Thampan, Raghava Varman

doi:10.1006/abbi.1995.1330

Cited by 12 publications

(6 citation statements)

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“…The very ®rst report on the NLS binding protein which mediates the nuclear entry of goat uterine estrogen receptor (gER) was made by Nirmala and Thampan [1995a]. It was ob- Freedman, 1999].…”

Section: Cytosol-to-nucleus Movement Of the Ermentioning

confidence: 99%

Proteins interacting with the mammalian estrogen receptor: proposal for an integrated model for estrogen receptor mediated regulation of transcription

Govind

Thampan

2001

J. Cell. Biochem.

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Two forms of estrogen receptor (ER) that exist in the mammalian uterus have been examined in this review. (1) ERalpha, or the classical estrogen receptor that is considered to influence the transcriptional process; (2) the non-activated estrogen receptor (naER), an alternative form of ER with no DNA binding function, localized in the plasma membrane. An integrated model is being proposed to highlight the functional roles of both receptors in transcriptional regulation. The proteins with which ER interacts during various stages of its existence are being examined. These stages include: (1) transport from the cytoplasm to the nucleus; (2) interaction with the nuclear transcription machinery; (3) involvement in post-transcriptional control mechanisms; and (4) degradation through ubiquitination. The proteins with which naER interacts during its plasma membrane-to-nucleus movement have also been identified; the results have not yet been published. Within the nucleus it dimerizes with a DNA-binding protein, the estrogen receptor activation factor (E-RAF). It is being proposed that the purpose behind the dimerization between naER and E-RAF is to transport E-RAF to the transcription initiation site as the naER in the heterodimer is a RNA-polymerase binding protein. Deglycosylated naER fails to dimerize with the E-RAF. Deglycosylation of the naER therefore dissociates the heterodimer and this transformed naER is now identified as nuclear estrogen receptor II (nER II). The dissociated E-RAF is free either to destabilize (E-RAF II) or stabilize (E-RAF I) the DNA while the naER remains bound to the RNA polymerase II. nER II phosphorylates certain subunits in RNA polymerase; the functional significance of this phosphorylation remains to be known.

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Section: Cytosol-to-nucleus Movement Of the Ermentioning

confidence: 99%

Proteins interacting with the mammalian estrogen receptor: proposal for an integrated model for estrogen receptor mediated regulation of transcription

Govind

Thampan

2001

J. Cell. Biochem.

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“…Nuclei treated with Triton X-100 failed to transport gER in the presence of p55 (Nirmala and Thampan, 1995b). It was also observed that a dialyzed detergent extract of the nuclei restored the transport function in Triton X-100 treated nuclei in the presence of p55.…”

Section: Introductionmentioning

confidence: 88%

“…The method developed by Nirmala and Thampan (1995a) was employed with modifications. Goat uterine estrogen receptor (gER), purified following the method reported by Zafar and Thampan (1993), was coupled to CNBr-activated Sepharose 4B (March et al, 1974).…”

Section: Purification Of P55mentioning

confidence: 99%

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Interdependence between a 55 kDa Protein (p55) and a 12 kDa Protein (p12) in Facilitating the Nuclear Entry of Goat Uterine Estrogen Receptor under Cell-Free Conditions

Padma¹,

Thampan²

2000

Biological Chemistry

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A 55 kDa nuclear localization signal binding protein (p55) is involved in the transport of the goat uterine estrogen receptor from the cytoplasm to the nuclear pore complex (NPC). p55 forms a complex with a 12 kDa protein (p12) which in turn becomes 'docked' at the NPC. The present study reports on the purification and functional characterization of p12. Both p55 and p12 are Mg2+-dependent ATPases. The protein-protein interactions that take place between these two molecules at the NPC cause an enhancement in the net ATPase activity associated with the protein complex. Presumably, this enhanced ATPase function helps in the final nuclear entry of the estrogen receptor; p55 remains associated with p12 at the nuclear entry site under these conditions.

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“…Studies carried out in our laboratory on the nuclear transport of goat uterine estrogen receptor α has clearly identified the involvement of two proteins: a 55 kDa protein (p55) that binds to the NLS on the ER and a 12 kDa protein (p12) that recognizes p55 on the one hand and a NPC protein on the other [Nirmala and Thampan, 1995; Sai Padma and Thampan, 2000; Sai Padma et al, 2000]. In the alternative estrogen receptor system that involves the naER, the NLS binding protein that mediates the transport of naER to the nucleus is a 58 kDa protein, p58.…”

mentioning

confidence: 99%

Proteins that mediate the nuclear entry of the goat uterine estrogen receptor activation factor (E‐RAF): Identification of a molecular basis for the inhibitory effect of progesterone on estrogen action

Govind

Sreekumar

Thampan

2003

J of Cellular Biochemistry

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A 66 kDa transport protein, tp66, has been identified as the protein that mediates the nuclear transport of the estrogen receptor activation factor (E-RAF). Indirect evidence shows that tp66 influences the transport of E-RAF mainly by recognizing the nuclear localization signals (NLS) on the latter. A 38 kDa nuclear pore complex protein (npcp38) has been identified to which tp66-E-RAF complex gets 'docked' prior to the nuclear entry of E-RAF. Progesterone binding to E-RAF serves to dissociate E-RAF from the tp66 thereby inhibiting the nuclear entry of E-RAF. The demonstration of the high affinity progesterone binding property of E-RAF adds credibility to the above findings. A change in conformation of E-RAF being brought about by progesterone binding is evident from the results of the circular dichroism (CD) analysis. This appears to be the fundamental reason behind the dissociation of the tp66-E-RAF complex under progesterone influence and provides a molecular basis for the estrogen 'antagonistic' action of progesterone. A nuclear run-on transcription assay clearly demonstrates the transcription-activation function of E-RAF II, also reaffirming the functional role of tp66 in the nuclear entry of E-RAF.

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A 55-kDa Protein (P55) of the Goat Uterus Mediates Nuclear Transport of the Estrogen-Receptor

Cited by 12 publications

References 0 publications

Proteins interacting with the mammalian estrogen receptor: proposal for an integrated model for estrogen receptor mediated regulation of transcription

Proteins interacting with the mammalian estrogen receptor: proposal for an integrated model for estrogen receptor mediated regulation of transcription

Interdependence between a 55 kDa Protein (p55) and a 12 kDa Protein (p12) in Facilitating the Nuclear Entry of Goat Uterine Estrogen Receptor under Cell-Free Conditions

Proteins that mediate the nuclear entry of the goat uterine estrogen receptor activation factor (E‐RAF): Identification of a molecular basis for the inhibitory effect of progesterone on estrogen action

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