Mutations in the NOT Genes or in the Translation Machinery Similarly Display Increased Resistance to Histidine Starvation
FRONTIERS IN GENETICS
Authors: Collart, Martine A.; Kassem, Sari; Villanyi, Zoltan
Abstract
The NOT genes encode subunits of the conserved Ccr4-Not complex, a global regulator of gene expression, and in particular of mRNA metabolism. They were originally identified in a selection for increased resistance to histidine starvation in the yeast S. cerevisiae. Recent work indicated that the Not5 subunit, ortholog of mammalian CNOT3, determines global translation levels by defining binding of the Ccr4-Not scaffold protein Not1 to ribosomal mRNAs during transcription. This is needed for optimal translation of ribosomal proteins. In this work we searched for mutations in budding yeast that were resistant to histidine starvation using the same selection that originally led to the isolation of the NOT genes. We thereby isolated mutations in ribosome-related genes. This common phenotype of ribosome mutants and not mutants is in good agreement with the positive role of the Not proteins for translation. In this regard, it is interesting that frequent mutations in RPL5 and RPL10 or in CNOT3 have been observed to accumulate in adult T-cell acute lymphoblastic leukemia (T-ALL). This suggests that in metazoans a common function implicating ribosome subunits and CNOT3 plays a role in the development of cancer. In this perspective we suggest that the Ccr4-Not complex, according to translation levels and fidelity, could itself be involved in the regulation of amino acid biosynthesis levels. We discuss how this could explain why mutations have been identified in many cancers.
Over-expressed genes detected by suppression subtractive hybridization in carcinoma derived from transformed 16HBE cells induced by BPDE
BIOMEDICAL AND ENVIRONMENTAL SCIENCES
Authors: An, SJ; Chen, JK; Liu, LL; Zhao, YF; Chen, XM
Abstract
Objective: To screen the over differentially expressed genes in carcinoma induced by BPDE-transformed 16HBE cells (16HBE-C cells). Methods: The suppression subtractive hybridization (SSH) method was performed to profile differentially expressed genes between 16HBE-C cells and 16HBE cells. The cDNA fragments of differentially expressed genes were inserted into TA cloning vector and transformed competent E. coli strain. Positive clones were randomly picked up and identified by the colony PCR method. Dot blot was used to test the same source with the tester. The differentially expressed cDNA fragments were sequenced and compared with known genes and EST database in Genbank. Results: Eight known genes were over-expressed in 16HBE-C cells including eukaryotic translation elongation factor 1 alpha 1, HIF-1 responsive RTP801, ribosomal protein L10 (RPL10), ribosomal protein S29 (RPS29), mitochondrion related genes, and laminin receptor 1. Three differentially expressed cDNA fragments could not be matched to the known genes but to the EST database. Conclusion: The SSH method can detect differentially expressed genes between 16HBE-C and 16HBE cells. BPDE-induced carcinogenesis may be related to alteration of at least eight known genes and three unknown genes. These expression data provide a clue to further cloning novel genes and studying functions in BPDE-induced carcinoma.