In Gene Expression, Length Matters
Human genomes harbour thousands of genes, each of which gives rise to proteins when it is active. But which inherent features of a gene determine its activity? Postdoctoral Scholar Pia Kjolhede Andersen and Senior Researcher Soren Lykke-Andersen from the Danish National Research Foundation's Centre for mRNP Biogenesis and Metabolism have now found that the distance between the gene start, termed the 'promoter', and the gene end, the 'terminator', is crucial for the activity of a protein-coding gene. If the distance is too short, the gene is transcriptionally repressed and the output is therefore severely decreased. This finding outlines a completely new functional interplay between gene ends.
Small genes utilise specialised terminators
Fortunately, most human protein-coding genes are long and are therefore not repressed by this mechanism. However, some genes, e.g. 'replication-dependent histone genes', are very short. How do such genes express their information at all? Interestingly, many of these differ from the longer protein-coding genes by containing specialised terminators. And in fact, if such a specialised terminator replaces a normal terminator in a short gene context, the short gene is no longer transcriptionally repressed. It therefore appears that naturally occurring short genes have evolved 'their own' terminators to achieve high expression levels.
The new findings add to a complex molecular network of intragenic communication and help us to understand the basic function of genes.