No abstract

By subtractive screening of a library made from mRNA of lipopolysaccharide (LPS)-stimulated mouse B lymphocytes we isolated cDNA-clones encoding the ribosomal protein L7. Human L7 mRNA was cloned from activated T-lymphocytes. Although no specific function of L7 in the translation apparatus is known as yet, it should be a critical one as indicated by its high degree of structural conservation during evolution and its regulated expression in lymphoid cells. Human and rodent L7 proteins carry sequences similar to the basic-region-leucine-zipper(BZIP)-motif of DNA-binding eucaryotic transcription factors. We show here that the region of L7 carrying the latter motif mediates L7-dimerization and stable binding to DNA and RNA. A preferential binding to RNA-structures is demonstrated.

VH-gene expression in hybridomas derived from lipopolysaccharide-activated B cells was analyzed. Isolated cytoplasmic RNA was hybridized to probes representing the 9 known VH-gene groups or subjected to mRNA sequencing. In the collection of hybridomas VH genes of all 9 groups are expressed at frequencies which in most correlate reasonably well with the relative complexities of the groups. In 51 out of 54 RNA samples VH-gene transcripts could be identified and corresponded to one of the known VH-gene groups. It therefore appears that the latter essentially represent the VH-gene cluster of the mouse.

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Four potentially productive and two non‐productive VDJ gene segments were isolated from the DNA of mouse B‐lymphocytes which had been polyclonally activated by bacterial lipopolysaccharide (LPS). Three VDJ regions exhibit VH genes which stem from two novel VH gene families. The complexity of these families is 5‐9 genes. One of the non‐productive VDJ regions exhibits a D segment which may have been generated by joining of two DSP2 segments. Both non‐productive VDJ regions appear to contain rearranged pseudo VH genes. Three potential somatic mutations distributed over two productive VDJ regions are observed.