The primary structure of rat ribosomal protein L34

RNAi-mediated RPL34 knockdown suppresses the growth of human gastric cancer cells

An increasing body of evidence suggests that ribosomal proteins may have ribosome-independent functions and may be involved in various physiological and pathological processes. To examine the role of ribosomal protein L34 (RPL34) in cancer transformation, we assessed its expression in gastric cancer cell lines and found it highly expressed. We further used lentivirus-mediated small interfering RNAs (siRNAs) to knockdown RPL34 expression in the human gastric cancer cell line SGC-7901. RNA interference (RNAi)-mediated inhibition of RPL34 expression in SGC-7901 cells significantly suppressed cell proliferation, increased apoptosis and arrested cells in the S phase. The results of the present study suggest that RPL34 plays a critical role in cell proliferation, cell cycle distribution and apoptosis of human malignant gastric cells.

Sequencing and characterization of the Xenopus laevis ribosomal protein L34 cDNA

In this paper, a cDNA homologous to the mammalian ribosomal protein (r-protein) L34 was isolated from a Xenopus laevis oocytes library and named XL34. It encodes a protein of 116 residues with an Mr of 13.2 kDa and a highly basic sequence. The nucleotide (nt) and deduced amino acid (aa) sequence have been compared with the L34 sequence from other species. This analysis showed that the L34 is a protein greatly conserved from prokaryotes to eukaryotes.XL34 mRNA is abundantly present in the whole cytoplasm of oocytes at stages 1 and 2.

Interaction of DA41, a DAN-binding protein, with the epidermal growth factor-like protein, S(1-5)

Recently, we have identified a new protein (DA41) which can associate with candidate tumor-suppressor DAN protein. In the present study, we have searched for DA41-interacting protein(s), using a yeast two-hybrid system. An adult rat lung cDNA library was screened by using a truncated form of DA41 (1-308) which lacks a DAN-binding region as bait. One of the positive clones, T16, contained a cDNA sequence of 1934 nucleotides with a single open reading frame of 493 amino acids. A data base search revealed that T16 exhibited a strong sequence similarity to the human epidermal growth factor (EGF)-like protein, S(1-5). The region encoding amino acids 155-232 of DA41 was identified for the interaction with T16. Since DAN and S(1-5) proteins are known to suppress and stimulate DNA synthesis, respectively, it is possible that functional interaction of DAN with S(1-5) through DA41 might play an important role(s) in the regulation of cell growth.

Mosquito ribosomal protein rpL31 resembles rat rpL34: cDNA and deduced amino acid sequence

An Aedes albopictus ribosomal protein rpL31 cDNA was sequenced, and found to encode a protein with homology to rat rpL34. The 544 bp mosquito cDNA contained an ATG start site, three in-frame termination codons, and an AATAAA polyadenylation signal. Mosquito rpL31 had a mass of 15,137 Da, a pI of 12.39 and contained 14.5% Arg and 14.5% Lys. PCR analyses with genomic DNA suggested the presence of a large intron near the 5'-end of the gene.

Developmental and environmental regulation of two ribosomal protein genes in tobacco

Two cDNA clones, TSC29 and TSC40, were isolated from a cDNA library prepared from three-day-old tobacco cell suspension grown to early exponential stage. DNA sequence analyses and database searches revealed that the TSC29 transcript encodes a protein which is highly homologous to eukaryotic 60S ribosomal (r)-protein L25 and that the TSC40 product is homologous to rat 60S r-protein L34. Southern blot analysis showed that the putative r-protein genes are members of multigene families. Transcript levels of both genes were most abundant in three-day-old cell suspension and declined in older cultures. Transcripts were also present in plant vegetative and reproductive organs. However, for TSC40 in particular, the mRNA levels were lower in plant organs than in three-day-old cell suspension. Stems and roots exhibited higher expression than leaves and flowers, indicating that these clones are differentially regulated in various cell types. Both genes were expressed at low levels in mature seeds but transcript levels significantly increased after one day of germination, remained at a high level until day 4, and declined after day 5. In situ localization experiments with germinating seedlings revealed that the TSC29 transcript was preferentially localized in root tips, epidermis, and endosperm. Wounding increased the steady-state mRNA amounts of these r-protein genes, and 2,4-dichlorophenoxyacetic acid and benzyladenine further increased the transcript level.