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RNA Export through the NPC in Eukaryotes.

Okamura M, Inose H, Masuda S - Genes (Basel) (2015)

Bottom Line: However, multiple export receptors are involved in the export of some RNAs, such as 60S ribosomal subunit.In addition to these export receptors, some adapter proteins are required to export RNAs.We also discuss the NPC anchoring-dependent mRNA export factors that directly recruit specific genes to the NPC.

View Article: PubMed Central - PubMed

Affiliation: Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan. okamura.masumi.66z@st.kyoto-u.ac.jp.

ABSTRACT
In eukaryotic cells, RNAs are transcribed in the nucleus and exported to the cytoplasm through the nuclear pore complex. The RNA molecules that are exported from the nucleus into the cytoplasm include messenger RNAs (mRNAs), ribosomal RNAs (rRNAs), transfer RNAs (tRNAs), small nuclear RNAs (snRNAs), micro RNAs (miRNAs), and viral mRNAs. Each RNA is transported by a specific nuclear export receptor. It is believed that most of the mRNAs are exported by Nxf1 (Mex67 in yeast), whereas rRNAs, snRNAs, and a certain subset of mRNAs are exported in a Crm1/Xpo1-dependent manner. tRNAs and miRNAs are exported by Xpot and Xpo5. However, multiple export receptors are involved in the export of some RNAs, such as 60S ribosomal subunit. In addition to these export receptors, some adapter proteins are required to export RNAs. The RNA export system of eukaryotic cells is also used by several types of RNA virus that depend on the machineries of the host cell in the nucleus for replication of their genome, therefore this review describes the RNA export system of two representative viruses. We also discuss the NPC anchoring-dependent mRNA export factors that directly recruit specific genes to the NPC.

No MeSH data available.


Related in: MedlinePlus

Nxf1-dependent mRNA export. Nascent pre-mRNA is spliced by the spliceosome, and then AlyRef, Uap56, and THO assemble into TREX-1. Uap56 can bind pre-mRNA independently of THO and AlyRef, but it is unclear whether the Uap56 that docks to TREX-1 is distinct from the Uap56 that binds pre-mRNA before binding to TREX-1; i.e., model (i) versus model (ii). Spliced mRNA within TREX-1 recruits a NXf1-Nxt1 heterodimer that allows the mRNA to traverse the nuclear pore complex (NPC). INM: inner nuclear membrane, ONM: outer nuclear membrane.
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genes-06-00124-f002: Nxf1-dependent mRNA export. Nascent pre-mRNA is spliced by the spliceosome, and then AlyRef, Uap56, and THO assemble into TREX-1. Uap56 can bind pre-mRNA independently of THO and AlyRef, but it is unclear whether the Uap56 that docks to TREX-1 is distinct from the Uap56 that binds pre-mRNA before binding to TREX-1; i.e., model (i) versus model (ii). Spliced mRNA within TREX-1 recruits a NXf1-Nxt1 heterodimer that allows the mRNA to traverse the nuclear pore complex (NPC). INM: inner nuclear membrane, ONM: outer nuclear membrane.

Mentions: TREX-1 consists of AlyRef (Aly/Thoc4/Ref/Bef), Uap56, Cip29, pDIP3, ZC11A, and the THO subcomplex, which consists of Thoc1 (THO1/Hpr1/p84), Thoc2 (THO2), Thoc3 (THO3/Tex1), Thoc5 (THO5/fSAP79), Thoc6 (THO6/fSAP35), and Thoc7 (THO7/fSAP24). Recruitment of TREX-1 and export of mRNP requires the 5' capping of pre-mRNA because CBP80, the component of the cap binding complex (CBC) that binds on the 5' capping site, interacts with AlyRef and the THO subcomplex [26,27]. Cip29 is also recruited to the mRNA in a cap- and splicing-dependent manner [28]. The DEAD-box RNA helicase Uap56 bridges THO and both AlyRef and Cip29 [28], but can bind pre-mRNA independent of AlyRef and THO. Uap56 is also a component of the TREX-1. It is unclear whether Uap56 binds pre-mRNA before TREX-1 formation and then joins TREX-1, or whether a distinct Uap56 is contained within TREX-1 [27]. TREX-1 is eventually recruited to the 5' end of pre-mRNA. The closed form of Nxf1 has a low affinity for RNA; Thoc5 and AlyRef induce a conformational change from the closed form of Nxf1 to the open form [5]. Binding of Nxf1 to mRNA via TREX-1 allows the mRNA to traverse the NPC (Figure 2). Yra1 of Saccharomyces cerevisiae (AlyRef in humans) interacts with the 3' end processing factor Pcf11 [29], and this binding enables coupling between transcription and 3' end processing.


RNA Export through the NPC in Eukaryotes.

Okamura M, Inose H, Masuda S - Genes (Basel) (2015)

Nxf1-dependent mRNA export. Nascent pre-mRNA is spliced by the spliceosome, and then AlyRef, Uap56, and THO assemble into TREX-1. Uap56 can bind pre-mRNA independently of THO and AlyRef, but it is unclear whether the Uap56 that docks to TREX-1 is distinct from the Uap56 that binds pre-mRNA before binding to TREX-1; i.e., model (i) versus model (ii). Spliced mRNA within TREX-1 recruits a NXf1-Nxt1 heterodimer that allows the mRNA to traverse the nuclear pore complex (NPC). INM: inner nuclear membrane, ONM: outer nuclear membrane.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4377836&req=5

genes-06-00124-f002: Nxf1-dependent mRNA export. Nascent pre-mRNA is spliced by the spliceosome, and then AlyRef, Uap56, and THO assemble into TREX-1. Uap56 can bind pre-mRNA independently of THO and AlyRef, but it is unclear whether the Uap56 that docks to TREX-1 is distinct from the Uap56 that binds pre-mRNA before binding to TREX-1; i.e., model (i) versus model (ii). Spliced mRNA within TREX-1 recruits a NXf1-Nxt1 heterodimer that allows the mRNA to traverse the nuclear pore complex (NPC). INM: inner nuclear membrane, ONM: outer nuclear membrane.
Mentions: TREX-1 consists of AlyRef (Aly/Thoc4/Ref/Bef), Uap56, Cip29, pDIP3, ZC11A, and the THO subcomplex, which consists of Thoc1 (THO1/Hpr1/p84), Thoc2 (THO2), Thoc3 (THO3/Tex1), Thoc5 (THO5/fSAP79), Thoc6 (THO6/fSAP35), and Thoc7 (THO7/fSAP24). Recruitment of TREX-1 and export of mRNP requires the 5' capping of pre-mRNA because CBP80, the component of the cap binding complex (CBC) that binds on the 5' capping site, interacts with AlyRef and the THO subcomplex [26,27]. Cip29 is also recruited to the mRNA in a cap- and splicing-dependent manner [28]. The DEAD-box RNA helicase Uap56 bridges THO and both AlyRef and Cip29 [28], but can bind pre-mRNA independent of AlyRef and THO. Uap56 is also a component of the TREX-1. It is unclear whether Uap56 binds pre-mRNA before TREX-1 formation and then joins TREX-1, or whether a distinct Uap56 is contained within TREX-1 [27]. TREX-1 is eventually recruited to the 5' end of pre-mRNA. The closed form of Nxf1 has a low affinity for RNA; Thoc5 and AlyRef induce a conformational change from the closed form of Nxf1 to the open form [5]. Binding of Nxf1 to mRNA via TREX-1 allows the mRNA to traverse the NPC (Figure 2). Yra1 of Saccharomyces cerevisiae (AlyRef in humans) interacts with the 3' end processing factor Pcf11 [29], and this binding enables coupling between transcription and 3' end processing.

Bottom Line: However, multiple export receptors are involved in the export of some RNAs, such as 60S ribosomal subunit.In addition to these export receptors, some adapter proteins are required to export RNAs.We also discuss the NPC anchoring-dependent mRNA export factors that directly recruit specific genes to the NPC.

View Article: PubMed Central - PubMed

Affiliation: Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan. okamura.masumi.66z@st.kyoto-u.ac.jp.

ABSTRACT
In eukaryotic cells, RNAs are transcribed in the nucleus and exported to the cytoplasm through the nuclear pore complex. The RNA molecules that are exported from the nucleus into the cytoplasm include messenger RNAs (mRNAs), ribosomal RNAs (rRNAs), transfer RNAs (tRNAs), small nuclear RNAs (snRNAs), micro RNAs (miRNAs), and viral mRNAs. Each RNA is transported by a specific nuclear export receptor. It is believed that most of the mRNAs are exported by Nxf1 (Mex67 in yeast), whereas rRNAs, snRNAs, and a certain subset of mRNAs are exported in a Crm1/Xpo1-dependent manner. tRNAs and miRNAs are exported by Xpot and Xpo5. However, multiple export receptors are involved in the export of some RNAs, such as 60S ribosomal subunit. In addition to these export receptors, some adapter proteins are required to export RNAs. The RNA export system of eukaryotic cells is also used by several types of RNA virus that depend on the machineries of the host cell in the nucleus for replication of their genome, therefore this review describes the RNA export system of two representative viruses. We also discuss the NPC anchoring-dependent mRNA export factors that directly recruit specific genes to the NPC.

No MeSH data available.


Related in: MedlinePlus