Nicotinic Acetylcholine Receptor Subunits α4 and α5 Associated with Smoking Behaviour and Lung Cancer Are Regulated by Upstream Open Reading Frames

Abstract

Nicotinic acetylcholine receptor subunits (nAChR) are associated with different aspects of smoking behaviour as well as with smoking related disorders. Several of these subunits have been found to be upregulated in smokers or differentially expressed in lung tumor cells. The mechanisms behind these observations are not known but assumed to be mainly post-transcriptional. Many post-transcriptional mechanisms are initiated by functionally relevant sequence motifs within untranslated gene regions, such as upstream open reading frames (uORFs). We performed a systematic search in all smoking-associated neuronal nAChR subunits and identified functionally relevant uORFs in CHRNA4 and CHRNA5. Luciferase experiments showed that these uORFs are able to significantly decrease protein expression. Our quantitative real-time PCR (qPCR) results strongly suggest that the observed effects originate at the translation rather than at the transcription level. Interestingly, the CHRNA4 uORF was only functionally relevant when expressed in the shorter isoform of this gene. Therefore, the data presented in this study strongly points towards an important role of uORFs within the 5′UTR of CHRNA4-isoform 1 and CHRNA5 as regulators of protein translation. Moreover, the shared uORF of CHRNA4-isoform 1/isoform 2 represents the first example of a sequence context-dependent uORF.

Post-transcriptional regulation of 5'-untranslated regions of human Transient Receptor Potential Vanilloid type-1 (TRPV-1) channels: role in the survival of glioma patients

“…The UTRs flanking the coding region in mature mRNA regulate translation or mRNA stability through diverse mechanisms, representing an extra level of gene expression control [ 26 - 28 ]. An increasing number of reports highlight the effect of simple sequence elements or secondary and tertiary structures of the 5’ UTR in affecting the translation efficiencies of proto-oncogenes or tumor suppressing genes [ 15 ], neurotransmitter receptors [ 29 ] and ion channels [ 30 ]. Elements in the 5’ UTR can mediate translational regulation via the 5’-cap or the secondary structure, and stable 5’ UTR structures can interfere with translation by reducing the accessibility for the translational machinery and ribosomal scanning [ 31 - 33 ].…”

The Relationship Between rs3212986C>A Polymorphism and Tumor Stage in Lung Cancer Patients

“…A study in 2013 investigated the effect of polymorphism in multiple genes on clinical outcomes in patients with colorectal cancer [8]. A study by Eggert et al in 2015 investigated the relationship of genetic variations in nucleotide binding oligomerization domain containing 1/ caspase recruitment domain4 (NOD1/CARD4) and NOD2/CARD15 genes with a high risk of lung cancer [12]. Results of our study showed that a lower response to chemotherapy is related to a modified haplotype of 8092 rather than a wild-type variant (1.94 x).…”

“…A study in Japan in 2013 investigated polymorphism in three genomic regions including the ERCC1 gene in colorectal cancer [8]. In numerous studies, mutation and polymorphism in the hot-spots of the ERCC1 gene in relation to the NER system have been mentioned in other cancers including glioma, cervix, and bladder in different populations [12-14]. This gene has a length of 71,534 base pairs and many transcript variants.…”