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TGF-beta induces the expression of SAP30L, a novel nuclear protein.

Lindfors K, Viiri KM, Niittynen M, Heinonen TY, Mäki M, Kainulainen H - BMC Genomics (2003)

Bottom Line: Differential display analysis resulted in the identification of a novel TGF-beta upregulated mRNA species, the Sin3-associated protein 30-like, SAP30L.The mRNA is expressed in several human tissues and codes for a nuclear protein of 183 amino acids 70% identical with Sin3 associated protein 30 (SAP30).The predicted nuclear localization signal of SAP30L is sufficient for nuclear transport of the protein although mutating it does not completely remove SAP30L from the nuclei.

View Article: PubMed Central - HTML - PubMed

Affiliation: Paediatric Research Centre, Tampere University Hospital, Tampere, Finland. katri.lindfors@uta.fi

ABSTRACT

Background: We have previously set up an in vitro mesenchymal-epithelial cell co-culture model which mimics the intestinal crypt villus axis biology in terms of epithelial cell differentiation. In this model the fibroblast-induced epithelial cell differentiation from secretory crypt cells to absorptive enterocytes is mediated via transforming growth factor-beta (TGF-beta), the major inhibitory regulator of epithelial cell proliferation known to induce differentiation in intestinal epithelial cells. The aim of this study was to identify novel genes whose products would play a role in this TGF-beta-induced differentiation.

Results: Differential display analysis resulted in the identification of a novel TGF-beta upregulated mRNA species, the Sin3-associated protein 30-like, SAP30L. The mRNA is expressed in several human tissues and codes for a nuclear protein of 183 amino acids 70% identical with Sin3 associated protein 30 (SAP30). The predicted nuclear localization signal of SAP30L is sufficient for nuclear transport of the protein although mutating it does not completely remove SAP30L from the nuclei. In the nuclei SAP30L concentrates in small bodies which were shown by immunohistochemistry to colocalize with PML bodies only partially.

Conclusions: By reason of its nuclear localization and close homology to SAP30 we believe that SAP30L might have a role in recruiting the Sin3-histone deacetylase complex to specific corepressor complexes in response to TGF-beta, leading to the silencing of proliferation-driving genes in the differentiating intestinal epithelial cells.

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Multiple alignment of SAP30L with its orthologues and SAP30 proteins of human and mouse. All six proteins are highly identical except for the 38 amino acids which appear in SAP30 of human, and mouse. Asterisks mark identical amino acids, colons and periods designate conservative substitutions.
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Figure 4: Multiple alignment of SAP30L with its orthologues and SAP30 proteins of human and mouse. All six proteins are highly identical except for the 38 amino acids which appear in SAP30 of human, and mouse. Asterisks mark identical amino acids, colons and periods designate conservative substitutions.

Mentions: Screening of a heart cDNA library in order to find the whole-length transcript resulted in identification of a positive clone with an insert of size 1.3 kB. When the clone was sequenced and compared to the sequence of an Image clone FLJ11526, the two sequences were found to be identical. Both clones code for a protein of 183 amino acids (Figure 3), which was named Sin3-associated protein 30 like, SAP30L. Prosite scan identified two putative N-glycosylation sites (NASF, amino acids 44–47 and NKSR, amino acids 168–171), one N-myristoylation site (GQSCCL, amino acids 26–31) and several phosphorylation sites for different kinases. The PsortII program predicted the SAP30L protein to be nuclear, the putative nuclear localization signal being KRKRK, ranging from amino acid 87 to 91 (Figure 3). A database search for homologous proteins showed that SAP30L has orthologues in several species (Figure 4). The corresponding mouse protein is 97% identical with the human SAP30L. The Xenopus protein is 85% identical along the first 150 amino acids after which they begin to diversify considerably while the Drosophila melanogaster orthologue is fairly identical along the whole protein, the identity being 52%. Interestingly, there was a human protein called SAP30, which was 70% identical with SAP30L. Amino acid comparison of SAP30L with SAP30 showed SAP30 to have in its N-terminus a 38-amino-acid stretch that was absent in SAP30L. The corresponding SAP30 protein was also found in mouse but not in other species.


TGF-beta induces the expression of SAP30L, a novel nuclear protein.

Lindfors K, Viiri KM, Niittynen M, Heinonen TY, Mäki M, Kainulainen H - BMC Genomics (2003)

Multiple alignment of SAP30L with its orthologues and SAP30 proteins of human and mouse. All six proteins are highly identical except for the 38 amino acids which appear in SAP30 of human, and mouse. Asterisks mark identical amino acids, colons and periods designate conservative substitutions.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC319701&req=5

Figure 4: Multiple alignment of SAP30L with its orthologues and SAP30 proteins of human and mouse. All six proteins are highly identical except for the 38 amino acids which appear in SAP30 of human, and mouse. Asterisks mark identical amino acids, colons and periods designate conservative substitutions.
Mentions: Screening of a heart cDNA library in order to find the whole-length transcript resulted in identification of a positive clone with an insert of size 1.3 kB. When the clone was sequenced and compared to the sequence of an Image clone FLJ11526, the two sequences were found to be identical. Both clones code for a protein of 183 amino acids (Figure 3), which was named Sin3-associated protein 30 like, SAP30L. Prosite scan identified two putative N-glycosylation sites (NASF, amino acids 44–47 and NKSR, amino acids 168–171), one N-myristoylation site (GQSCCL, amino acids 26–31) and several phosphorylation sites for different kinases. The PsortII program predicted the SAP30L protein to be nuclear, the putative nuclear localization signal being KRKRK, ranging from amino acid 87 to 91 (Figure 3). A database search for homologous proteins showed that SAP30L has orthologues in several species (Figure 4). The corresponding mouse protein is 97% identical with the human SAP30L. The Xenopus protein is 85% identical along the first 150 amino acids after which they begin to diversify considerably while the Drosophila melanogaster orthologue is fairly identical along the whole protein, the identity being 52%. Interestingly, there was a human protein called SAP30, which was 70% identical with SAP30L. Amino acid comparison of SAP30L with SAP30 showed SAP30 to have in its N-terminus a 38-amino-acid stretch that was absent in SAP30L. The corresponding SAP30 protein was also found in mouse but not in other species.

Bottom Line: Differential display analysis resulted in the identification of a novel TGF-beta upregulated mRNA species, the Sin3-associated protein 30-like, SAP30L.The mRNA is expressed in several human tissues and codes for a nuclear protein of 183 amino acids 70% identical with Sin3 associated protein 30 (SAP30).The predicted nuclear localization signal of SAP30L is sufficient for nuclear transport of the protein although mutating it does not completely remove SAP30L from the nuclei.

View Article: PubMed Central - HTML - PubMed

Affiliation: Paediatric Research Centre, Tampere University Hospital, Tampere, Finland. katri.lindfors@uta.fi

ABSTRACT

Background: We have previously set up an in vitro mesenchymal-epithelial cell co-culture model which mimics the intestinal crypt villus axis biology in terms of epithelial cell differentiation. In this model the fibroblast-induced epithelial cell differentiation from secretory crypt cells to absorptive enterocytes is mediated via transforming growth factor-beta (TGF-beta), the major inhibitory regulator of epithelial cell proliferation known to induce differentiation in intestinal epithelial cells. The aim of this study was to identify novel genes whose products would play a role in this TGF-beta-induced differentiation.

Results: Differential display analysis resulted in the identification of a novel TGF-beta upregulated mRNA species, the Sin3-associated protein 30-like, SAP30L. The mRNA is expressed in several human tissues and codes for a nuclear protein of 183 amino acids 70% identical with Sin3 associated protein 30 (SAP30). The predicted nuclear localization signal of SAP30L is sufficient for nuclear transport of the protein although mutating it does not completely remove SAP30L from the nuclei. In the nuclei SAP30L concentrates in small bodies which were shown by immunohistochemistry to colocalize with PML bodies only partially.

Conclusions: By reason of its nuclear localization and close homology to SAP30 we believe that SAP30L might have a role in recruiting the Sin3-histone deacetylase complex to specific corepressor complexes in response to TGF-beta, leading to the silencing of proliferation-driving genes in the differentiating intestinal epithelial cells.

Show MeSH
Related in: MedlinePlus