Stress-induced tRNA-derived RNAs: a novel class of small RNAs in the primitive eukaryote Giardia lamblia.
Giardia lamblia is an early diverging and evolutionarily successful protozoan as it can enter into a dormant cyst stage from a vegetative trophozoite. During dormant stage, its metabolic rate decreases dramatically. However, to date, the regulatory molecules participating in the initiation and maintenance of this process have not been fully investigated. In this study, we have identified a class of abundant small RNAs named sitRNAs, which are approximately 46 nucleotides in length and accumulate in G. lamblia encysting cultures. Remarkably, they are derived from the 3' portion of fully matured tRNAs by cleavage of the anticodon left arm, with the 3' terminal CCA triplex still connected. During differentiation, only a limited portion of mature tRNAs is cleaved, but this cleavage occurs almost in the entire tRNA family. sitRNAs begin to accumulate as early as 3 h after initiation of encystation and are maintained at a relatively stable level during the whole process, exhibiting an expression peak at around 24 hr. Our studies further show that sitRNAs can be induced by several other stress factors, and in the case of serum deprivation, both tRNAs and sitRNAs degrade rapidly, with the accumulation of tRNA being halved. Our results may provide new insight into a novel mechanism for stressed G. lamblia to regulate gene expression globally.
Li
Yan
Y
Key Laboratory of Gene Engineering of the Ministry of Education, State Key Laboratory for Biocontrol, Zhongshan University, Guangzhou 510275, P. R. China.
Luo
Jun
J
Zhou
Hui
H
Liao
Jian-You
JY
Ma
Li-Ming
LM
Chen
Yue-Qin
YQ
Qu
Liang-Hu
LH
D000818:Animals; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free; D016829:Giardia lamblia / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D016053:RNA, Protozoan / Q000737:chemistry / Q000145:classification / Q000378:metabolism*; D012343:RNA, Transfer / Q000737:chemistry* / Q000378:metabolism; D022661:RNA, Untranslated / Q000737:chemistry / Q000145:classification / Q000378:metabolism*; D013696:Temperature; D053058:Trophozoites / Q000378:metabolism
D016895:Culture Media, Serum-Free; D016053:RNA, Protozoan; D022661:RNA, Untranslated; D012343:RNA, Transfer