Size matters for non-coding RNAs

You may already be familiar with the Tsix/Xist non-coding RNA system which is responsible for the inactivation of the second X chromosome in females. The system is quite elegant, and uses long non coding RNA with complementary sequence to "coat" the X chromosome which starts a chain of rearrangements leading to condensation and Lyonisation. This way the female genome can compensate its transcriptional output to match that of the male.

Well it turns out that there are 940 other long (>100bp) non-coding RNAs in humans. What is their function? Are they also involved in modulating chromosome architecture? This study (subscription required) looked at a set of abundantly expressed, evolutionarily conserved long non coding RNA (l-ncRNA). The authors decided to look at their expression in normal versus cancer tissues, and found differences in levels and the presence of mutations. They conclude:

"The function of these NCTs is currently unknown. Their abundance, tremendous sequence conservation and aberrant expression in many ovarian and breast cancers suggest that they not only play an important role in normal cellular growth and immune response, but also in the development of cancer. Consistent potential mutations at specific nucleotides within some of these NCTs also suggest that these alterations are not random, but have an important functional role in cancer development."

• Perez et al. Hum. Mol. Genet..2008; 17: 642-655

  PMID: 18006640