All organisms need a very accurate system to regulate the activity of their genes. To do this, they have various elements that are responsible for this control. An example are the so-called insulators, which are DNA sequences that allow eukaryotic cells to organise their chromatin in adjacent but independent expression domains; neighbouring genes are isolated so they can co-exist and modulate their own expression without interfering with others.
In a study published in PNAS, researchers at the Centro Nacional de Biotecnología (CNB-CSIC), in collaboration with the Andalusian Centre for Developmental Biology in Seville and the Georgia Institute of Technology in the USA, have reported that certain human DNA sequences, known as MIR (mammalian-wide interspersed repeat) elements, act as insulators.
MIR elements, which are formed by several repetitions of the same DNA sequence, are found in the non-coding genome, which is not translated into protein. According to the authors, some miR elements can recruit the transcription machinery of other genes and regulate the degree of DNA compaction to make it more or less accessible to this machinery. They thus prevent or promote expression of adjacent genes based on the needs of the cell.
"We have shown this new function of the miR family using bioinformatic tools, in vitro assays with human cells, and in vivo studies in zebra fish," explains Lluis Montoliu, principal investigator of the CNB group that participated in the study.
- Jianrong Wang, Cristina Vicente-García, Davide Seruggia, Eduardo Moltó, Ana Fernandez-Miñán, Ana Neto, Elbert Lee, José Luis Gómez-Skarmeta, Lluís Montoliu, Victoria V. Lunyak, and I. King Jordan. MIR retrotransposon sequences provide insulators to the human genome. PNAS, DOI: 10.1073/pnas.1507253112