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Preliminary Analysis of NMD Pathway in Euplotes octocarinatus
Shi Wenxin, Wang Mei, Chai Yangli, Lü Jia, Zhang Zhiyun, Wang Gang, Chai Baofeng*
Key Laboratory of Chemical Biology and Molecular Engineering, Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China
Abstract: Nonsense-mediated mRNA decay (NMD) represents an important mechanism to monitor mRNA quality， which can distinguish and degrade aberrant transcripts harbouring premature termination codons (PTCs). However， the detailed mechanism is not fully understood. Ciliates are regarded as the earliest branch of eukaryotes， and studying on its NMD can help us elucidating the mechanism and evolution of this important process. We identified a group of NMD factors from genome of ciliates Euplotes octocarinatus， EuUPF1， EuUPF2， EuY14a， EuY14b and EuMAGO. We demonstrated that EuUPF1 and EuUPF2 interplayed mediated by CH domain of EuUPF1 and C-terminal domain of EuUPF2. Two paralogs of Y14， designed as EuY14a and EuY14b were identified， and both of them interacted with EuMAGO protein， a core factor of exon junction complex (EJC)， as a marker complex of NMD in eukaryotes. Furthermore， we displayed that interaction between UPF1 and aberrant mRNA mediated directly by Y14a and or mediated by UPF2 and EJC (MAGO， Y14b， Y14a)， respectively. Thus we hypothesized that both EJCindependent and EJC-dependent NMD pathways coexist in ciliates Euplotes cell， based on the consideration that the content of intron in genome of Euplotes is less than that of higher eukaryote and more than that of lower organisms such as fungi. However， the detailed mechanism of this NMD pathway remains to be investigated.
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