The Klein Group research centers on the molecular machinery that degrades mRNAs in chloroplasts.
About the group
A typical cell contains thousands of different mRNA species whose lifetimes can differ from a few minutes to several hours or days. Furthermore, it has been found that lifetimes of individual mRNA populations can be up- and down-regulated by internal and external cues. Despite its importance for determining levels of transcripts and of gene expression, the molecular basis for differences in lifetimes of mRNAs is largely unknown. Sequence elements important for stabilizing or destabilizing transcripts have been found in 5’ and 3’ untranslated regions of mRNAs but how these elements function in controlling RNA longevity remains elusive.
We have delineated short RNA-stabilizing sequences near the 5’ terminus of mRNAs in chloroplasts and showed that these sequences have to fold into a specific RNA secondary structure in order to function in RNA stabilization. Mutations in the 5’ region of mRNAs that prevent folding of the sequences into their native conformation render the transcripts extremely unstable.
At present our research centers on the molecular machinery that degrades mRNAs in chloroplasts. To date, a number of proteins involved in mRNA turnover have been identified. One of these proteins is an RNA pyrophosphohydrolase (RppH) which converts triphosphorylated RNA 5’ ends into monophosphorylated ends, thereby probably initiating mRNA degradation. We have identified an RppH homolog in Chlamydomonas and are currently studying its role in mRNA degradation in the algal chloroplast.