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Research articles

ScienceAsia 40(2014): 400-404 |doi: 10.2306/scienceasia1513-1874.2014.40.400


Distinctive roles of human Argonaute1, 2, 3, and 4 proteins on LINE-1 methylation and regulation of intragenic LINE-1-containing genes


Piyapat Pin-ona, Apiwat Mutirangurab,*

 
ABSTRACT:     Argonaute proteins (AGOs) are evolutionarily conserved and ubiquitously expressed in all higher eukaryotes. They participate in cell differentiation, transposon silencing, and other important functions. AGOs play key roles in the gene-silencing pathways guided by small RNAs. There are many human AGOs. However, redundancy and the distinctive roles of different AGOs have not been well characterized. Previously, we demonstrated that AGO2 down-regulates the expression of genes containing hypomethylated long interspersed nuclear elements (LINE-1s). Here, we evaluate the expression of genes containing LINE-1 in AGO1-4-knocked down HEK293 cells. Furthermore, we measured the methylation levels of AGO1-4-bound LINE-1s. Genes containing LINE-1s in AGO1, -2, -3 or -4-knocked down HEK293 cells showed prevented up-regulation, increased up-regulation, unchanged regulation and prevented up-regulation, respectively. Interestingly, AGO1-4 bound to LINE-1 differently in terms of the methylation level. Although the methylation level of AGO1 and -4-bound LINE-1s was not different from that of the genome, AGO2- and AGO3-bound LINE-1s were hypomethylated. Our experiments demonstrate the distinctive epigenetic roles of AGO1-4 in regulating genes containing LINE-1s.

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a Inter-department Program of Biomedical Sciences, Faculty of Graduate School, Chulalongkorn University, Bangkok 10330 Thailand
b Centre of Excellence in Molecular Genetics of Cancer and Human Diseases, Department of Anatomy, Faculty of Medicine, Chulalongkorn University, Bangkok 10330 Thailand

* Corresponding author, E-mail: mapiwat@chula.ac.th

Received 22 Aug 2014, Accepted 2 Dec 2014