Nucleic Acids Research, Vol 25, Issue 2 395-402, Copyright © 1997 by Oxford University Press
BD Keiper and RE Rhoads
Eukaryotic cellular mRNAs contain a cap at their 5'-ends, but some viral
and cellular mRNAs bypass the cap-dependent mechanism of translation
initiation in favor of internal entry of ribosomes at specific RNA
sequences. Cap-dependent initiation requires intact initiation factor eIF4G
(formerly eIF-4gamma, eIF-4Fgamma or p220), whereas internal initiation can
proceed with eIF4G cleaved by picornaviral 2A or L proteases. Injection of
recombinant coxsackievirus B4 protease 2A into Xenopus oocytes led to
complete cleavage of endogenous eIF4G, but protein synthesis decreased by
only 35%. Co- injection of edeine reduced synthesis by >90%, indicating
that eIF4G- independent synthesis involved ongoing initiation. The spectrum
of endogenous proteins synthesized was very similar in the presence or
absence of intact eIF4G. Translation of exogenous rabbit globin mRNA, by
contrast, was drastically inhibited by eIF4G cleavage. The N- terminal
cleavage product of eIF4G (cpN), which binds eIF4E, was completely degraded
within 6-12 h, while the C-terminal cleavage product (cpC), which binds to
eIF3 and eIF4A, was more stable over the same period. Thus, translation
initiation of most endogenous mRNAs inXenopusoocytes requires no eIF4G, or
perhaps only cpC, suggesting a cap-independent mechanism.
ARTICLES
Cap-independent translation initiation in Xenopus oocytes
Department of Biochemistry and Molecular Biology, Louisiana State University Medical Center, 1501 King's Highway, Shreveport, LA 71130- 3932, USA.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  T. M. Hinton, M. J. Coldwell, G. A. Carpenter, S. J. Morley, and V. M. Pain Functional Analysis of Individual Binding Activities of the Scaffold Protein eIF4G J. Biol. Chem., January 19, 2007; 282(3): 1695 - 1708. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. J. Coldwell and S. J. Morley Specific Isoforms of Translation Initiation Factor 4GI Show Differences in Translational Activity Mol. Cell. Biol., November 15, 2006; 26(22): 8448 - 8460. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Castello, E. Alvarez, and L. Carrasco Differential Cleavage of eIF4GI and eIF4GII in Mammalian Cells: EFFECTS ON TRANSLATION J. Biol. Chem., November 3, 2006; 281(44): 33206 - 33216. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Montero, C. F. Arias, and S. Lopez Rotavirus Nonstructural Protein NSP3 Is Not Required for Viral Protein Synthesis. J. Virol., September 1, 2006; 80(18): 9031 - 9038. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 W. Zhou, G. M. Edelman, and V. P. Mauro A positive feedback vector for identification of nucleotide sequences that enhance translation PNAS, May 3, 2005; 102(18): 6273 - 6278. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 I. Burgui, T. Aragon, J. Ortin, and A. Nieto PABP1 and eIF4GI associate with influenza virus NS1 protein in viral mRNA translation initiation complexes J. Gen. Virol., December 1, 2003; 84(12): 3263 - 3274. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
X. Zhao, B. J. Lamphear, D. Xiong, K. Knowlton, and R. E. Rhoads Protection of Cap-dependent Protein Synthesis in Vivo and in Vitro with an eIF4G-1 Variant Highly Resistant to Cleavage by Coxsackievirus 2A Protease J. Biol. Chem., February 7, 2003; 278(7): 4449 - 4457. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. P. Mauro and G. M. Edelman The ribosome filter hypothesis PNAS, September 17, 2002; 99(19): 12031 - 12036. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. A. Chappell, G. M. Edelman, and V. P. Mauro A 9-nt segment of a cellular mRNA can function as an internal ribosome entry site (IRES) and when present in linked multiple copies greatly enhances IRES activity PNAS, February 15, 2000; 97(4): 1536 - 1541. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
I. Novoa and L. Carrasco Cleavage of Eukaryotic Translation Initiation Factor 4G by Exogenously Added Hybrid Proteins Containing Poliovirus 2Apro in HeLa Cells: Effects on Gene Expression Mol. Cell. Biol., April 1, 1999; 19(4): 2445 - 2454. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. Kerekatte, B. D. Keiper, C. Badorff, A. Cai, K. U. Knowlton, and R. E. Rhoads Cleavage of Poly(A)-Binding Protein by Coxsackievirus 2A Protease In Vitro and In Vivo: Another Mechanism for Host Protein Synthesis Shutoff? J. Virol., January 1, 1999; 73(1): 709 - 717. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
I. Ventoso, A. Barco, and L. Carrasco Mutational Analysis of Poliovirus 2Apro. DISTINCT INHIBITORY FUNCTIONS OF 2Apro ON TRANSLATION AND TRANSCRIPTION J. Biol. Chem., October 23, 1998; 273(43): 27960 - 27967. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. L. Gillian-Daniel, N. K. Gray, J. Åström, A. Barkoff, and M. Wickens Modifications of the 5' Cap of mRNAs during Xenopus Oocyte Maturation: Independence from Changes in Poly(A) Length and Impact on Translation Mol. Cell. Biol., October 1, 1998; 18(10): 6152 - 6163. [Abstract] [Full Text]
|
|
|
|
|
|
A. Gradi, Y. V. Svitkin, H. Imataka, and N. Sonenberg Proteolysis of human eukaryotic translation initiation factor eIF4GII, but not eIF4GI, coincides with the shutoff of host protein synthesis after poliovirus infection PNAS, September 15, 1998; 95(19): 11089 - 11094. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. A. Chappell, G. C. Owens, and V. P. Mauro A 5' Leader of Rbm3, a Cold Stress-induced mRNA, Mediates Internal Initiation of Translation with Increased Efficiency under Conditions of Mild Hypothermia J. Biol. Chem., September 28, 2001; 276(40): 36917 - 36922. [Abstract] [Full Text] [PDF]
|
|