Protein sequence requirements for function of the human T-cell leukemia virus type 1 Rex nuclear export signal delineated by a novel in vivo randomization-selection assay.

Abstract

The Rex protein of human T-cell leukemia virus type 1, like the functionally equivalent Rev protein of human immunodeficiency virus type 1, contains a leucine-rich activation domain that specifically interacts with the human nucleoporin-like Rab/hRIP cofactor. Here, this Rex sequence is shown to function also as a protein nuclear export signal (NES). Rex sequence libraries containing randomized forms of the activation domain/NES were screened for retention of the ability to bind Rab/hRIP by using the yeast two-hybrid assay. While the selected sequences differed widely in primary sequence, all were functional as Rex activation domains. In contrast, randomized sequences that failed to bind Rab/hRIP lacked Rex activity. The selected sequences included one with homology to the Rev activation domain/NES and a second that was similar to the NES found in the cellular protein kinase inhibitor alpha. A highly variant, yet fully active, activation domain sequence selected on the basis of Rab/hRIP binding retained full NES function even though this sequence preserved only a single leucine residue. In contrast, nonfunctional activation domain mutants that were unable to bind Rab/hRIP had also lost NES function. These data demonstrate that NES activity is a defining characteristic of the activation domains found in the Rev/Rex class of retroviral regulatory proteins and strongly support the hypothesis that the Rab/hRIP cofactor plays a critical role in mediating the biological activity of these NESs. In addition, these data suggest a consensus sequence for NESs of the Rev/Rex class.

• Authors: H P Bogerd, R A Fridell, R E Benson, J Hua, B R Cullen
• Journal: Molecular and cellular biology (Mol Cell Biol) Vol. 16 Issue 8 Pg. 4207-14 (Aug 1996) ISSN: 0270-7306 [Print] United States
• PMID: 8754820 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• AGFG1 protein, human
• Carrier Proteins
• Gene Products, rex
• Nuclear Pore Complex Proteins
• RNA-Binding Proteins
• Recombinant Proteins

Topics

• Amino Acid Sequence
• Binding Sites
• Biological Transport
• Carrier Proteins (metabolism)
• Cell Nucleus (metabolism)
• Gene Products, rex (metabolism)
• Human T-lymphotropic virus 1 (metabolism)
• Molecular Sequence Data
• Nuclear Pore Complex Proteins
• Protein Binding
• RNA-Binding Proteins (metabolism)
• Recombinant Proteins
• Sequence Alignment
• Sequence Homology, Amino Acid
• Structure-Activity Relationship