Title:Two Novel Heparin-binding Vascular Endothelial Growth Factor Splices, L-VEGF144 and L-VEGF138, are Expressed in Human Glioblastoma Cells
Volume: 13
Issue: 3
Author(s): Chiung-Chyi Shen, Wen-Yu Cheng, Ming-Tsang Chiao, Yea-Jiuan Liang, Tsuo-Fei Mao and Bai-Shuan Liu
Affiliation:
Keywords:
Angiogenesis, vascular endothelial growth factor, novel VEGF isoforms, differential splicing, nuclear localization.
Abstract: The expression levels of different vascular endothelial growth factor A (VEGF) isoforms are associated with
the angiogenesis and the patient’s prognoses in human cancers. Ribosomes specifically scan from 5’ to 3’ CUG initiation
codon in the long 5’-untranslated region (5’-UTR) of the VEGF mRNA, resulting in the generation of high mol wt VEGF
isoform [call large VEGF (L-VEGF)]. Alternative splicing of VEGF mRNA transcripts results in several isoforms with
distinct properties that are dependent up their exon compositions. In this study, we observed two novel kinds of splicing
VEGF isoforms that transcripted at the first upstream CUG codon, and which we have named large-VEGF144 (LVEGF144),
and large-VEGF138 (L-VEGF138). The expression levels of messenger RNA for the different VEGF splice
forms were analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR). After DNA sequencing, the genetic
structure of L-VEGF144 involved not only a partial exon 1, exon 6a, and exons 7-8, but also an unique 108- nucleotides
insertion of VEGF intron 5 interposed between exon 1 and exon 6. At the same time, L-VEGF144 lacked most of the Nterminal
fragments (exons 1-5). We further found that a specific detection model could easily and rapidly confirm the
presence of L-VEGF144 mRNA fragments in the biopsies or cell lines via RT-PCR assay. In addition, we used visible
fluorescent fusion proteins to prove that both L-VEGF144 and L-VEGF138 have nuclear localization ability. Taken together,
the findings of this study indicate that, unlike previously identified isoforms, these novel VEGF isoforms are likely
to suggest a further level of complexity in the angiogenic process.
