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The Mex67p-mediated nuclear mRNA export pathway is conserved from yeast to human
J Katahira1, K Strässer, A Podtelejnikov
1BZH, Biochemie-Zentrum Heidelberg, Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany.
Abstract:
Human TAP is an orthologue of the yeast mRNA export factor Mex67p. In mammalian cells, TAP has a preferential intranuclear localization, but can also be detected at the nuclear pores and shuttles between the nucleus and the cytoplasm. TAP directly associates with mRNA in vivo, as it can be UV-crosslinked to poly(A)+ RNA in HeLa cells. Both the FG-repeat domain of nucleoporin CAN/Nup214 and a novel human 15 kDa protein (p15) with homology to NTF2 (a nuclear transport factor which associates with RanGDP), directly bind to TAP. When green fluorescent protein (GFP)-tagged TAP and p15 are expressed in yeast, they localize to the nuclear pores. Strikingly, co-expression of human TAP and p15 restores growth of the otherwise lethal mex67::HIS3/mtr2::HIS3 double knockout strain. Thus, the human TAP-p15 complex can functionally replace the Mex67p-Mtr2p complex in yeast and thus performs a conserved role in nuclear mRNA export.
Insights
Human TAP protein and its partner p15 can substitute for yeast mRNA export factors. This discovery highlights a conserved mechanism for nuclear mRNA export across species.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- Human TAP (a homolog of yeast Mex67p) is involved in mRNA export.
- TAP localizes to the nucleus, nuclear pores, and cytoplasm, associating with poly(A)+ RNA.
- TAP interacts with nucleoporin CAN/Nup214 and a novel protein, p15.
Purpose of the Study:
- To investigate the function of human TAP and its interacting protein p15 in mRNA export.
- To determine if the human TAP-p15 complex can functionally replace the yeast Mex67p-Mtr2p complex.
Main Methods:
- UV-crosslinking of TAP to poly(A)+ RNA in HeLa cells.
- Co-expression of GFP-tagged human TAP and p15 in yeast.
- Assessing the growth of a double knockout yeast strain (mex67::HIS3/mtr2::HIS3) upon co-expression.
Main Results:
- Human TAP directly binds to mRNA in vivo.
- Human TAP and p15 localize to nuclear pores when expressed in yeast.
- Co-expression of human TAP and p15 rescued the lethal phenotype of the yeast mex67::HIS3/mtr2::HIS3 double knockout.
Conclusions:
- The human TAP-p15 complex can functionally substitute for the yeast Mex67p-Mtr2p complex.
- This demonstrates a conserved role for TAP-p15 in nuclear mRNA export between humans and yeast.