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Characterization of the internal IRES element of the zebrafish connexin55.5 reveals functional implication of the polypyrimidine tract binding protein

BACKGROUND: Connexin55.5 (Cx55.5) is a gap junction protein with horizontal cell-restricted expression in zebrafish accumulating at dendritic sites within the receptor-horizontal cell complex in form of hemichannels where light-dependent plasticity occurs. This connexin is the first example of a gap...

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Autores principales: Ul-Hussain, Mahboob, Dermietzel, Rolf, Zoidl, Georg
Formato: Texto
Lenguaje:English
Publicado: BioMed Central 2008
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2579433/
https://www.ncbi.nlm.nih.gov/pubmed/18947383
http://dx.doi.org/10.1186/1471-2199-9-92
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author Ul-Hussain, Mahboob
Dermietzel, Rolf
Zoidl, Georg
author_facet Ul-Hussain, Mahboob
Dermietzel, Rolf
Zoidl, Georg
author_sort Ul-Hussain, Mahboob
collection PubMed
description BACKGROUND: Connexin55.5 (Cx55.5) is a gap junction protein with horizontal cell-restricted expression in zebrafish accumulating at dendritic sites within the receptor-horizontal cell complex in form of hemichannels where light-dependent plasticity occurs. This connexin is the first example of a gap junction protein processed to form two protein isoforms from a monocistronic message by an IRES mediated process. The nuclear occurrence of a carboxy-terminal fragment of this protein provides evidence that this gap junction protein may participate in a putative cytoplasmic to nuclear signal transfer. RESULTS: We characterized the IRES element of Cx55.5 in terms of sequence elements necessary for its activity and protein factor(s), which may play a role for its function. Two stretches of polypyrimidine tracts designated PPT1 and PPT2 which influence the IRES activity of this neuronal gap junction protein were identified. Selective deletion of PPT1 results in an appreciable decrease of the IRES activity, while the deletion of PPT2 results in a complete loss. RNA-EMSA and UV-cross linking experiments showed that protein complexes bind to this IRES element, of which the polypyrimidine tract binding protein (PTB) was identified as one of the interacting partners with influence on IRES activity. These results indicate that PTB conveys a role in the regulation of the IRES activity of Cx55.5. CONCLUSION: Our findings indicate that the activity of the IRES element of the neuronal gap junction protein Cx55.5 is subject of regulation through flanking polypyrimidine tracts, and that the non-canonical trans-activation factor PTB plays an essential role in this process. This observation is of considerable importance and may provide initial insight into molecular-functional relationships of electrical coupling in horizontal cells.
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spelling pubmed-25794332008-11-06 Characterization of the internal IRES element of the zebrafish connexin55.5 reveals functional implication of the polypyrimidine tract binding protein Ul-Hussain, Mahboob Dermietzel, Rolf Zoidl, Georg BMC Mol Biol Research Article BACKGROUND: Connexin55.5 (Cx55.5) is a gap junction protein with horizontal cell-restricted expression in zebrafish accumulating at dendritic sites within the receptor-horizontal cell complex in form of hemichannels where light-dependent plasticity occurs. This connexin is the first example of a gap junction protein processed to form two protein isoforms from a monocistronic message by an IRES mediated process. The nuclear occurrence of a carboxy-terminal fragment of this protein provides evidence that this gap junction protein may participate in a putative cytoplasmic to nuclear signal transfer. RESULTS: We characterized the IRES element of Cx55.5 in terms of sequence elements necessary for its activity and protein factor(s), which may play a role for its function. Two stretches of polypyrimidine tracts designated PPT1 and PPT2 which influence the IRES activity of this neuronal gap junction protein were identified. Selective deletion of PPT1 results in an appreciable decrease of the IRES activity, while the deletion of PPT2 results in a complete loss. RNA-EMSA and UV-cross linking experiments showed that protein complexes bind to this IRES element, of which the polypyrimidine tract binding protein (PTB) was identified as one of the interacting partners with influence on IRES activity. These results indicate that PTB conveys a role in the regulation of the IRES activity of Cx55.5. CONCLUSION: Our findings indicate that the activity of the IRES element of the neuronal gap junction protein Cx55.5 is subject of regulation through flanking polypyrimidine tracts, and that the non-canonical trans-activation factor PTB plays an essential role in this process. This observation is of considerable importance and may provide initial insight into molecular-functional relationships of electrical coupling in horizontal cells. BioMed Central 2008-10-23 /pmc/articles/PMC2579433/ /pubmed/18947383 http://dx.doi.org/10.1186/1471-2199-9-92 Text en Copyright © 2008 Mahboob-Ul-Hussain et al; licensee BioMed Central Ltd. http://creativecommons.org/licenses/by/2.0 This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( (http://creativecommons.org/licenses/by/2.0) ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Research Article
Ul-Hussain, Mahboob
Dermietzel, Rolf
Zoidl, Georg
Characterization of the internal IRES element of the zebrafish connexin55.5 reveals functional implication of the polypyrimidine tract binding protein
title Characterization of the internal IRES element of the zebrafish connexin55.5 reveals functional implication of the polypyrimidine tract binding protein
title_full Characterization of the internal IRES element of the zebrafish connexin55.5 reveals functional implication of the polypyrimidine tract binding protein
title_fullStr Characterization of the internal IRES element of the zebrafish connexin55.5 reveals functional implication of the polypyrimidine tract binding protein
title_full_unstemmed Characterization of the internal IRES element of the zebrafish connexin55.5 reveals functional implication of the polypyrimidine tract binding protein
title_short Characterization of the internal IRES element of the zebrafish connexin55.5 reveals functional implication of the polypyrimidine tract binding protein
title_sort characterization of the internal ires element of the zebrafish connexin55.5 reveals functional implication of the polypyrimidine tract binding protein
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2579433/
https://www.ncbi.nlm.nih.gov/pubmed/18947383
http://dx.doi.org/10.1186/1471-2199-9-92
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