Characterization of cDNA clones encoding the human homologue of Saccharomyces cerevisiae ribosomal protein L30

Altered gene expression in melanocytes exposed to 4-tertiary butyl phenol (4-TBP): upregulation of the A2b adenosine receptor 1

Exposure to phenolic agents contributes to the development of occupational vitiligo. Proposed as a causative factor for leukoderma in vivo, the para-substituted phenol 4-tertiary butyl phenol was chosen to investigate early cellular events responsible for selective disappearance of melanocytes from the epidermis of individuals sensitive to such agents. To this end, differential display of melanocyte mRNA isolated from three separate cultures was performed following a 12 h exposure of cells to 250 microM 4-tertiary butyl phenol or to vehicle alone. Fragments of cDNA representing differentially expressed messages were cloned and subsequently confirmed by reverse dot blotting. Alignment analysis revealed that the L30 ribosomal protein was upregulated by the treatment, potentially reflecting altered levels of protein synthesis in response to stress. In addition, a gene sequence upregulated following exposure to 4-tertiary butyl phenol was identified as the A2b receptor (a P1 receptor for adenosine). Differential expression of this gene was confirmed in an RNase protection assay. By reverse transcription-polymerase chain reaction, the gene was shown to be expressed in keratinocytes and fibroblasts as well. Flow cytometry confirmed differential expression in melanocytes and fibroblasts, but not in keratinocytes. Interestingly, it has been reported that P1 purinoceptor stimulation can induce apoptosis. This is in concordance with results reported elsewhere demonstrating induction of apoptosis by 4-tertiary butyl phenol in human melanocytes, as well as with morphologic changes observed in this study in cells exposed to 250 microM 4-tertiary butyl phenol for 72 h. In conclusion, differential display is useful to establish melanocyte components involved in the cellular response to phenolic agents.

Cloning and characterisation of cDNA encoding the Trypanosoma brucei ribosomal protein L24

A cDNA encoding ribosomal protein L24 was amplified by PCR from the protozoan parasite, Trypanosoma brucei. The 621 nucleotide cDNA had an open reading frame of 375 nucleotides, predicting a highly basic protein of 125 aa. Database searches revealed 33-40% identity between the T. brucei RPL24 protein and several eukaryotic RPL24 homologues. Southern blot analysis indicated that the gene was present as a single copy, and a transcript of approximately 620 nucleotides was detected in procyclic forms of the parasite. Interestingly, T. brucei PRL24 is the smallest eukaryotic RPL24 protein described to date. It is also the most divergent of the known kinetoplastid ribosomal proteins.