|Diagram of the essential subunit of |
human RNA polymerase I, II, III
by Nevit Dilmen
Three different RNA polymerases are employed in order to make all of the different types of RNA required for normal cell function. The structure of RNA polymerase II, which makes mRNA, has been known for over 10 years but the structure of RNA polymerase I, which is responsible for making RNA which will form ribosomes has been elusive, until now. Details of the structure of RNA polymerase I may be found in a recent publication in the journal Nature. The report is a collaboration between German and Spanish scientists entitled: 'Crystal structure of the 14-subunit RNA polymerase I.'
One aspect that had previously confounded the study of RNA polymerase I is its size, which is much larger than RNA polymerase II. The results of the 3-D structure indicate that some of the larger size is the result of additional modules that are very similar in structure to proteins that assist RNA polymerase II function. Having these modules constantly attached may, in part, explain why RNA polymerase I produces RNA faster than RNA polymerase II. However, the permanent association provides the cell with fewer means of regulating RNA polymerase II function.
To find out more about this discovery you can read the ScienceDaily entry: Bigger, Better, Faster: 3D Structure Reveals Protein's Swiss-Army Knife Strategy