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Cap-Independent Translation Initiation of Apaf-1 mRNA Based on a Scanning Mechanism Is Determined by Some Features of the Secondary Structure of Its 5′ Untranslated Region

D. E. Andreev, S. E. Dmitriev, I. M. Terenin, and I. N. Shatsky*

Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; fax: (495) 939-3181; E-mail: shatsky@genebee.msu.su

* To whom correspondence should be addressed.

Received September 6, 2012; Revision received October 18, 2012
We have earlier shown that the 5′-untranslated region (5′ UTR) of the mRNA coding for activation factor of apoptotic peptidase 1 (Apaf-1) can direct translation in vivo by strictly 5′ end-dependent way even in the absence of m7G-cap. Dependence of translational efficiency on the cap availability for this mRNA turned out to be relatively low. In this study we demonstrate that this surprising phenomenon is determined the 5′-proximal part (domains I and II) of highly structured Apaf-1 5′ UTR. Remarkably, domain II by itself was able to reduce dependence of the mRNA on the cap on its transferring to a short 5′ UTR derived from a standard vector. We suggest that the low cap-dependence inherent to some cellular mRNAs may have an important physiological significance under those stress conditions when the function of cap-binding factor eIF4E is impaired.
KEY WORDS: protein biosynthesis, translational control, cellular IRES-elements, cap-independent translation, Apaf-1 mRNA

DOI: 10.1134/S0006297913020041