Characterization of the unique intron - exon junctions of Euglena gene(s) encoding the polyprotein precursor to the light-harvesting chlorophyll a/b binding protein of photosystem II

Authors

Umesh Shyamsunder Muchhal, University of Nebraska - Lincoln
Steven D. Schwartzbach, University of Nebraska - Lincoln

Date of this Version

1994

Citation

Nucleic Acids Research, 1994, Vol. 22, No. 25 5737-5744

Comments

Published by Oxford University Press. Used by permission.

Abstract

The precursor to the Euglena light harvesting chlorophyll a/b binding protein of photosystem 11 (LHCPII) Is a polyprotein containing multiple copies of LHCPII covalently joined by a decapeptide linker. cDNA and genomic clones encoding the 5 and 3' end of a 6.6 kb LHCPII mRNA were sequenced. A 3.1 kb genomic region encoding 1.05 kb of the 5' end of LHCPII mRNA contains 4 introns. A 7.6 kb genomic region encoding 3.3 kb of the 3' end of LHCPII mRNA contains 10 introns. The 5' and 3' ends of the 14 Identified Euglena introns lacked the conserved dinucleotides (5'-GT and AG-3') found at the termini of virtually every characterized nuclear pre-mRNA intron. A common consensus splice site selection sequence could not be identified. The Euglena introns do not have the structural characteristics of group I and group 11 introns. The only structural feature common to all Euglena introns was the ability of short stretches of nucleotides at the 5' and 3' ends of the introns to base pair, forming a stable stem-loop with the 5' and 3' splice site juxtaposed for splicing but displaced by 2 nucleotides. The 26 nucleotide sequence at the 5' end of LHCPII mRNA is absent from the genomic sequence and identical to the 5' end of one of the small Euglena SLRNAs indicating that it is post-transcriptionally added by trans-splicing.