Purification, primary structure and molecular cloning of a rat ribosomal protein showing homology with yeast ribosomal protein YL34

Murine HIP/L29 is a heparin-binding protein with a restricted pattern of expression in adult tissues

Heparin/heparan sulfate (Hp/HS)-binding proteins are implicated in a variety of cell biological processes including cell adhesion, modulation of blood coagulation, and cytokine/growth factor action. Hp/HS-interacting protein (HIP) has been identified in various adult tissues in humans. HIP supports high affinity, selective binding to Hp/HS, promotes cell adhesion, and modulates blood coagulation activities via Hp/HS-dependent mechanisms. Herein, a murine ortholog of human HIP is described that is 78.8% identical to human HIP and 99.8% identical at the cDNA level and identical at the amino acid level to a previously described murine ribosomal protein, L29. Western blot analyses and immunohistological staining with affinity-purified antibodies generated against two distinct peptide sequences of murine HIP/L29 indicate that HIP/L29 is differentially expressed in adult murine tissues and cell types. In the normal murine mammary epithelial cell line, NMuMG, HIP/L29 is enriched in the 100,000 x g particulate fraction. HIP/L29 can be solubilized from the 100,000 x g particulate fraction with 0.8 M NaCl, suggesting that it is a peripheral membrane protein. HIP/L29 directly binds 125I-Hp in gel overlay assays and requires 0.75 M NaCl for elution from Hp-agarose. In addition, recombinant murine HIP expressed in Escherichia coli binds Hp in a saturable and highly selective manner, compared with other glycosaminoglycans including dermatan sulfate, chondroitin sulfate, keratan sulfate, and hyaluronic acid. Collectively, these data indicate that murine HIP/L29, like its human ortholog, is a Hp-binding protein expressed in a restricted manner in adult tissues.

cDNA cloning and expression of HIP, a novel cell surface heparan sulfate/heparin-binding protein of human uterine epithelial cells and cell lines

Heparan sulfate proteoglycans and their corresponding binding sites have been suggested to play an important role during the initial attachment of murine blastocysts to uterine epithelium and human trophoblastic cell lines to uterine epithelial cell lines. Previous studies on RL95 cells, a human uterine epithelial cell line, had characterized a single class of cell surface heparin/heparan sulfate (HP/HS)-binding sites. Three major HP/HS-binding peptide fragments were isolated from cell surfaces by tryptic digestion, and partial amino-terminal amino acid sequence for each peptide fragment was obtained (Raboudi, N., Julian, J., Rohde, L. H., and Carson, D. D. (1992) J. Biol. Chem. 267, 11930-11939). In the current study, using approaches of reverse transcription-polymerase chain reaction and cDNA library screening, we have cloned and expressed a novel, cell surface HP/HS-binding protein, named HP/HS interacting protein (HIP), from RL95 cells. The full-length cDNA of HIP encodes a protein of 159 amino acids with a calculated molecular mass of 17,754 Da and pI of 11.75. Transfection of HIP full-length cDNA into NIH-3T3 cells demonstrated cell surface expression and a size similar to that of HIP expressed by human cells. Predicted amino acid sequence indicates that HIP lacks a membrane spanning region and has no consensus sites for glycosylation. Northern blot analysis detected a single transcript of 1.3 kilobases in both total RNA and poly(A+) RNA. Examination of human cell lines and normal tissues using both Northern blot and Western blot analyses revealed that HIP is expressed at different levels in a variety of human cell lines and normal tissues but absent in some cell lines and some cell types of normal tissues examined. HIP has relatively high homology (approximately 80% both at the levels of nucleotide and protein sequence) to a rodent ribosomal protein L29. Thus, members of the L29 family may be displayed on cell surfaces where they may participate in HP/HS binding events.

Cloning a pseudogene and cDNA encoding a 17-kDa ribosomal protein from mouse: structure and regulation of expression

An rp lambda 5 cDNA encoding a ribosomal protein (r-protein) and a pseudogenic form of the corresponding gene (rp lambda 7) have been cloned from mouse. This cDNA codes for a highly basic protein of 160 amino acids (aa) with a deduced M(r) of 17,601, and most likely represents the species homolog of a recently cloned rat cDNA, which has been proposed to encode a homolog of the yeast r-protein, YL43. The entire rp lambda 5 gene encompasses less than 1.5 kb of genomic DNA and apparently is composed of only two exons, as deduced from sequence comparison with its very similar pseudogenic variant, rp lambda 7. Southern analysis, using the rp lambda 5 cDNA as a probe, indicates the existence of a great number of highly related sequences in the mouse genome. The mRNA for rp lambda 5 is approximately 800 nucleotides (nt) long and is found to be ubiquitously expressed at high levels in embryonic and adult mouse tissues, as shown by Northern and in situ analyses. Retinoic acid (RA) seems to have a moderate down-regulatory effect on this mRNA in differentiating P19 embryonal carcinoma cells. Several degenerate/nondegenerate RA-response element (RARE) motifs are found within 560 bp upstream from the degenerate start codon in rp lambda 7. However, it is unknown whether this RA effect is exerted at the transcriptional and/or posttranscriptional levels.

Retinoic acid-response elements with a highly repetitive structure isolated by immuno-selection from genomic DNA

In vitro binding sites of retinoic acid receptors (RARs) were isolated from mouse genomic DNA by immunoprecipitation of receptor/DNA complexes. PuG(G/T)TCA half-site motifs, which constitute RA-responsive elements (RAREs), were identified in the immuno-selected fragments (ISFs), some of which contained highly repetitive arrangements of this motif. Genomic Southern analysis of a number of ISFs showed them to be of a single or low copy number. Several, but not all, ISFs acted as ligand-dependent RAREs in transient transfection assays. Two ISFs with repetitive RARE motifs responded preferentially to 9-cis retinoic acid-liganded retinoid X receptor in the presence or absence of co-transfected RAR, while little activation was seen with RAR alone in the presence of either all-trans or 9-cis retinoic acid. Another ISF, containing consensus TATA and CAAT box motifs, was shown to have RA-inducible promoter activity. The results suggest a high degree of promiscuity in response element recognition by retinoid receptors.