ABSTRACT
Approximately two-thirds of the 55 to 60 plastid ribosomal proteins are encoded in the nucleus. Since the protein products of each of these genes are needed in equal amounts for ribosome assembly, their expression may be coordinately regulated by common mechanisms. To begin to understand how the expression of these genes is regulated, we have isolated cDNA and genomic clones for three plastid ribosomal protein genes from an Arabidopsis thaliana library. The genes rps17, rpl9 and rpl15, encoding plastid ribosomal proteins CS17, CL9 and CL15, respectively, are located in the nuclear genome and Southern blot data suggest that each is a single copy gene in A. thaliana. Northern blot data show that transcripts from rps17, rpl9 and rpl15 are much more abundant in leaves and stems than they are in roots. The nucleotide sequences of each of these three genes were determined and their transcriptional initiation sites identified. rps17 transcripts have multiple 5' ends suggesting that they are initiated at multiple sites or are post-transcriptionally processed at their 5' end. rpl9 and rpl15 apparently have unique transcriptional initiation sites but are post-transcriptionally processed to remove six and three introns, respectively, from their primary transcripts. We have examined the genomic sequences for motifs that may be important for the proper expression of these genes. A 7 bp sequence motif, whose consensus is 5'-AGGCCCA-3', flanked by AT-rich regions was identified between 38 and 73 nucleotides upstream of the rps17, rpl9 and rpl15 transcriptional initiation sites.
Subject(s)
Arabidopsis Proteins , Plant Proteins/genetics , Plants/genetics , Ribosomal Proteins/genetics , Amino Acid Sequence , Base Sequence , Blotting, Northern , Blotting, Southern , Cloning, Molecular , Molecular Sequence Data , Plant Proteins/chemistry , Ribosomal Proteins/chemistryABSTRACT
The nucleotide sequence of a mouse ribosomal protein gene, identified by hybridization with the gene encoding the Drosophila ribosomal (r-) protein 49, was determined by cloning in the phage M13 and dideoxy sequencing. The mouse gene, L32', is a member of the multigene family encoding mammalian r-protein L32. L32' is a processed gene that could encode a 135 amino acid protein similar to that of mouse L32 and Drosophila r-protein 49.
Subject(s)
Pseudogenes , Ribosomal Proteins/genetics , Animals , Base Sequence , Cloning, Molecular , Drosophila/genetics , Humans , Mice , Molecular Sequence Data , Multigene Family , Nucleic Acid Hybridization , Restriction MappingABSTRACT
The processed gene L32', a member of the mouse gene family for ribosomal protein L32, could encode a 135 amino acid protein nearly identical to L32. The 5'-flanking region of the gene contains CAAT and TATA sites at positions commonly found in expressed genes. The L32' gene lies within highly methylated, DNase I-insensitive chromatin of mouse L1210 cells. Although S1 nuclease digestion studies suggested that an L32' transcript might be produced, an oligonucleotide probe specific for L32' mRNA, and RNase digestion of a cRNA probe to L32', indicated fewer than 0.1 L32' transcripts/cell. These results demonstrate that extreme caution is required when measuring transcription from related genes.
