engleski

Various 5' Untranslated Region cis-Regulatory Elements Regulate the Expression of Human PTCH1b Gene

PTCH1 tumor-suppressor gene encodes for a transmembrane receptor with a negative regulatory role in Hedgehog-Gli signaling pathway. PTCH1 germline mutations cause Gorlin syndrome which is characterized by developmental abnormalities and tumor susceptibility. Most of malformations are caused by PTCH1 haploinsufficiency, indicative of fine-tuning needed to properly regulate pathway activity. In this research we examined how 5’ untranslated region (5’UTR) regulates the expression of PTCH1 transcript 1b. All found PTCH1b 5’UTR cis-regulatory elements were studied by various in silico tools and gene reporter assays, based on pGL3-P and pRuF constructs. Found elements were: 5’UTR length (188- and 300bp-long) ; CGG-trinucleotide repeat polymorphism (5-8 repeats) ; upstream open reading frames (uORFs), and internal ribosome entry site (IRES) predicted within last 76 nucleotides of PTCH1b 5’UTR. Results showed that shorter 5’UTR significantly increased firefly luciferase (fluc) activity, with a subtle reduction with higher repeat number. Longer 5’UTR led to much reduced activity, without a difference among repeats. Fluc mRNA levels showed that both 5’UTRs significantly increased reporter gene transcription. Site-directed mutagenesis proved hypothesis that two potential uORFs, present only in longer 5’UTR, might account for observed reduction in reporter activity. Both 5’UTRs significantly increased firefly luciferase activity of pRuF vectors, with no difference among repeats ; while fluc activity was significantly reduced after removing predicted IRES motif. All our results point to exceptionally complex and so far unexplored role of 5’UTR in the regulation of PTCH1b expression, whilst the existence of an IRES would enable PTC1 protein to be synthesized under conditions when general level of protein synthesis is reduced, such as in hypoxia.

PTCH1; 5' UTR; CGG repeats; uORF; IRES

nije evidentirano