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Human fibulin‐4: analysis of its biosynthetic processing and mRNA expression in normal and tumour tissues
Author(s) -
Gallagher William M.,
Greene Lisa M.,
Ryan Michael P.,
Sierra Véronique,
Berger Anne,
Laurent-Puig Pierre,
Conseiller Emmanuel
Publication year - 2001
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(00)02389-9
Subject(s) - fibulin , biology , messenger rna , gene , microbiology and biotechnology , translation (biology) , gene expression , endoplasmic reticulum , genetics
Here, we report the identification of a human orthologue of fibulin‐4, along with analysis of its biosynthetic processing and mRNA expression levels in normal and tumour tissues. Comparative sequence analysis of fibulin‐4 cDNAs revealed apparent polymorphisms in the signal sequence that could account for previously reported inefficient secretion in fibulin‐4 transfectants. In vitro translation of fibulin‐4 mRNA revealed the presence of full‐length and truncated polypeptides, the latter apparently generated from an alternative translation initiation site. Since this polypeptide failed to incorporate into endoplasmic reticulum membrane preparations, it was concluded that it lacked a signal sequence and thus could represent an intracellular form of fibulin‐4. Using fluorescence in situ hybridisation analysis, the human fibulin‐4 gene was localised to chromosome 11q13, this region being syntenic to portions of mouse chromosomes 7 and 19. Considering the fact that translocations, amplifications and other rearrangements of the 11q13 region are associated with a variety of human cancers, the expression of human fibulin‐4 was evaluated in a series of colon tumours. Reverse transcription‐polymerase chain reaction analysis of RNA from paired human colon tumour and adjacent normal tissue biopsies showed that a significant proportion of tumours had ∼2–7‐fold increases in the level of fibulin‐4 mRNA expression. Taken together, results reported here suggest that an intracellular form of fibulin‐4 protein may exist and that dysregulated expression of the fibulin‐4 gene is associated with human colon tumourigenesis.