A GC-rich sequence within the 5' untranslated region of human basonuclin mRNA inhibits its translation

Structural and Functional Insights into Targeting GCCG Sites in the EGFR Promoter by Two DNA Intercalators to Inhibit Breast Cancer Metastasis

Chemotherapeutic drugs are commonly used to treat cancers lacking targeted therapy options. However, their low specificity limits their treatment effectiveness. We report here that the cooperative binding of doxorubicin (Dox) with actinomycin D (ActD) enhances the specificity for consecutive GCCG sites in DNA. Using X-ray crystallography, we determined the crystal structure of ActD and Dox bound to d(AGCCGT)2 DNA. ActD intercalation at the GpC site induces a novel Dox binding mode at the adjacent CpG step. This ensures a snug fit, avoids steric clashes, and enhances the specificity. Transcriptome analysis revealed that combining Dox with ActD synergistically down-regulates EGFR in TNBC cells. Additionally, it reduces EGFR promoter activity. In vivo, the combination significantly suppresses tumor growth and outperforms the standard Dox and cyclophosphamide regimen in inhibiting metastasis. This study highlights targeting the activated EGFR pathway with sequence-specific DNA-targeting drug combinations as a potential TNBC treatment.

Nucleotide variation and physical mapping of ribosomal genes using FISH in genus Tor (Pisces, Cyprinidae)

Molecular cytogenetic studies were carried out for localization of 18S and 5S ribosomal DNAs on chromosomes of three cyprinid fish species viz., T. khudree, T. mussullah and T. mosal mahanadicus using two color fluorescence in situ hybridization (FISH). All the species typically possessed 100 diploid chromosomes with minor variation in karyo-morphology. The 18S rDNA signals were observed on two pair of chromosomes in T. khudree and T. mussullah, and three pairs in T. mosal mahanadicus. The location of 18S signals also showed affinity to silver nitrate and chromomycin A3 staining. Similarly, variation in localization of 5S rDNA among the three species has been detected with the presence of FISH signals on one pair of chromosome in T. khudree and T. mussullah, and on two pairs in T. mosal mahanadicus. These molecular markers could be used as species specific markers for taxonomic identification and can further add in understanding the dynamics of genome organization and karyotypic evolution of these species. The 18S rDNA region was sequenced that generated 1811, 1810 and 1776 bp long 18S sequence in T. khudree, T. mussullah and T. mosal mahanadicus, respectively. The 18S rDNA sequence showed 95-98% identity among the subject species. Similarly, 5S sequencing generated 203 bp long fragments in these species with 100% identity in coding and 9.63% variability in non-transcribed spacer regions. The nucleotide sequence variations could be used for understanding the genetic diversity and will add new informative characters in comparative genomics. These results, in general, would enhance the value and interpretation of ecological assessment data for conservation of Tor species.

Gli proteins up-regulate the expression of basonuclin in Basal cell carcinoma

Tumorigenesis is frequently accompanied by enhanced rRNA transcription, but the signaling mechanisms responsible for such enhancement remain unclear. Here, we report evidence suggesting a novel link between deregulated Hedgehog signaling and the augmented rRNA transcription in cancer. Aberrant activation of the Hedgehog pathway in keratinocytes is a hallmark of basal cell carcinoma (BCC), the most common cancer in light-skinned individuals. We show that Gli proteins, downstream effectors of the Hedgehog pathway, increase expression of a novel rRNA gene (rDNA) transcription factor, basonuclin, whose expression is markedly elevated in BCCs. The promoter of the human basonuclin gene contains a Gli-binding site, which is required for Gli protein binding and transcriptional activation. We show also that the level of 47S pre-rRNA is much higher in BCCs than in normal epidermis, suggesting an accelerated rRNA transcription in the neoplastic cells. Within BCC, those cells expressing the highest level of basonuclin also exhibit the greatest increase in 47S pre-rRNA, consistent with a role for basonuclin in increasing rRNA transcription in these cells. Our data suggest that Hedgehog-Gli pathway enhances rRNA transcription in BCC by increasing basonuclin gene expression.

Variants of the 5'-untranslated region of the bovine growth hormone receptor mRNA: isolation, expression and effects on translational efficiency

The growth hormone receptor (GHR) gene in cattle is expressed as multiple GHR mRNA variants that differ in the 5'-untranslated region (5'-UTR). Three GHR mRNA 5'-UTR variants (named 1A, 1B, and 1C) were isolated in previous studies. Six additional GHR mRNA 5'-UTR variants (named 1D, 1E, 1F, 1G, 1H, and 1I) were discovered in the present study by using rapid amplification of cDNA ends (RACE). Ribonuclease protection assays (RPA) indicated that variant 1A was exclusively expressed in liver, variant 1F was expressed in liver and muscle, and most of the remaining GHR 5'-UTR variants were expressed in a variety of tissues including liver and muscle. The RPA also indicated that in liver and skeletal muscle, two important GH target tissues, the most abundant GHR mRNA 5'-UTR variants were 1A and 1B (liver) and 1B and 1C (muscle), respectively. In vitro translation assays indicated that the GHR 5'-UTR variants also differed in their effects on the translation of a luciferase reporter mRNA. Notably, the GHR 5'-UTR 1B, which is a highly expressed GHR 5'-UTR variant in vivo, strongly inhibited translation of the luciferase reporter mRNA. The observations in the present study suggest that GHR expression in the bovine may be controlled by translational mechanisms in addition to complex transcriptional mechanisms.