Research

Research

Research Description

The Beyer Lab is interested in the basic cellular processes of ribosomal RNA (rRNA) transcription and ribosome biogenesis. We use an unusual electron microscopic approach (the Miller chromatin spreading method) that allows us to directly visualize active rRNA genes. All of our current studies are carried out in the yeast, Saccharomyces cerevisiae. Shown here is a low magnification view of DNA released from a budded yeast cell.

nuclear chromatin spilling from a lysed budded yeast cell

 

Many of our studies are focused on deciphering the regulation of ribosomal RNA transcription because it is primarily this process that determines ribosome synthesis rate, which is tightly coupled to cell growth rate.  We study transcriptional regulation by analyzing such parameters as the number of active rRNA genes in a nucleolus, transcription initiation and elongation rates for active genes, and chromatin structures correlated with various genetic activities.

Fig2-chromatin structure of active and inactive rDNA genes

In a typical approach, we first characterize parameters of interest in control cells and then compare them to the same parameters in cells with a genetic alteration of interest.  For the study of ribosome biogenesis, which begins while ribosomal RNA is being transcribed, we characterize structural details of early intermediates in small ribosomal subunit assembly that form on nascent transcripts; (as shown in the micrograph below). The type of data we obtain is very difficult to obtain using standard molecular biology approaches due to the multi-copy nature of rRNA genes and to the very short-lived nature of ribosome intermediates, but is very informative regarding molecular mechanism and structure.

: progressive co-transcriptional stages in packaging and cleavage of nascent rRNA transcripts

In recent studies, we examined the role of specific transcription initiation and elongation factors, as well as the role of topoisomerase activity, in ribosomal RNA transcription. Ongoing studies include continued analysis of co-transcriptional events in small ribosomal subunit assembly, examination of the role of individual RNA polymerase subunits in rRNA transcription, and analysis of polymerase trafficking on active genes.