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Plant 7SL RNA genes belong to type 4 of RNA polymerase III‐ dependent genes that are composed of mixed promoters
Author(s) -
Yukawa Yasushi,
Felis Martha,
Englert Markus,
Stojanov Michael,
Matoušek Jaroslav,
Beier Hildburg,
Sugiura Masahiro
Publication year - 2005
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2005.02430.x
Subject(s) - promoter , gene , genetics , polymerase , biology , signal recognition particle rna , rna , rna polymerase , rna polymerase ii , rna polymerase iii , non coding rna , gene expression
Summary The genes transcribed by RNA polymerase III (pol III) display a great diversity in terms of promoter structure and are placed in four groups accordingly. Type 3 subset of pol III genes has promoter elements which reside entirely upstream of the coding region of the gene whereas type 4 consists of genes with mixed promoters that enclose intra‐ and extragenic regulatory sequences. Plant 7SL RNA genes have been previously classified as type 3 of pol III genes requiring an upstream sequence element and a canonical TATA box for transcriptional activity in transfected plant protoplasts. We have identified two novel functional control regions within the coding region of an Arabidopsis 7SL RNA gene (At7SL‐1) that resemble tRNA gene‐specific A and B boxes with respect to sequence and position. Single and multiple nucleotide substitutions in either of these regions resulted in a pronounced reduction of transcription activity in tobacco nuclear extract that was not caused by a decreased stability as shown by decay kinetics of wild type and mutant RNA transcripts. These findings suggest that plant 7SL RNA genes should be actually placed in type 4 of pol III‐transcribed genes. As a consequence of substantially different upstream promoters utilized by plant and human pol III, in vitro transcription of 7SL RNA genes in heterologous systems is severely impaired. A chimeric human 7SL RNA gene that contains the 5′ flanking region up to position −300 of At7SL‐1 is yet transcribed with a reduced efficiency in tobacco extract when compared with the plant wild‐type gene, supporting the notion that internal regulatory elements contribute to full activity.