Cloning and Sequence Analysis of 5S Ribosomal RNA Gene(s) and Associated Intergenic Spacer Regions in Carica Species

The 5S ribosomal RNA gene(s) and their associated intergenic spacer regions were amplified from Carica papaya and Carica quercifolia by polymerase chain reaction. Both Carica species exhibited differently sized amplification products. Sequence analysis of these PCR products revealed that the 5S rRNA genes are arranged as tandem repeats in these regions. Sequence data revealed that the 5S rRNA gene from Carica quercifolia was 119 bp in length. Sequence variation was observed in various 5S rRNA gene copies cloned from Carica quercifolia. Only truncated 5S rRNA gene but with its full spacer region was recovered from Carica papaya. Interestingly, intergenic spacer sequence cloned from Carica papaya contained two specific domains, a 30bp “CT” rich domain exhibiting 95-100% homology to several human chromosomes and a domain matching with mitrocomin precursor, a photo-protein from Mitrocoma cellularia. The role of 5S rRNA gene and their spacer regions in discerning the germplasm and in adaptation of the species is discussed.

Chemosensitization of prostate cancer stem cells in mice by angiogenin and plexin-B2 inhibitors

Cancer stem cells (CSCs) are an obstacle in cancer therapy and are a major cause of drug resistance, cancer recurrence, and metastasis. Available treatments, targeting proliferating cancer cells, are not effective in eliminating quiescent CSCs. Identification of CSC regulators will help design therapeutic strategies to sensitize drug-resistant CSCs for chemo-eradication. Here, we show that angiogenin and plexin-B2 regulate the stemness of prostate CSCs, and that inhibitors of angiogenin/plexin-B2 sensitize prostate CSCs to chemotherapy. Prostate CSCs capable of self-renewal, differentiation, and tumor initiation with a single cell inoculation were identified and shown to be regulated by angiogenin/plexin-B2 that promotes quiescence and self-renewal through 5S ribosomal RNA processing and generation of the bioactive 3′-end fragments of 5S ribosomal RNA, which suppress protein translation and restrict cell cycling. Monoclonal antibodies of angiogenin and plexin-B2 decrease the stemness of prostate CSCs and sensitize them to chemotherapeutic agents in vitro and in vivo.