scholarly journals An adenovirus type 5 E1A protein with a single amino acid substitution blocks wild-type E1A transactivation.

1987 ◽  
Vol 7 (3) ◽  
pp. 1004-1011 ◽  
Author(s):  
G M Glenn ◽  
R P Ricciardi
Keyword(s):  
Amino Acid ◽  
Amino Acid Substitution ◽  
Adenovirus Type ◽  
Single Amino Acid Substitution ◽  
Single Amino Acid ◽  
Wild Type ◽  
Missense Mutant ◽  
E1a Gene ◽  
Adenovirus Type 5 ◽  
E1a Protein

The E1A gene of adenovirus type 5 encodes a 289-amino-acid (289R) protein that transactivates early adenovirus promoters. We showed that the 289R protein of the E1A missense mutant gene hr5 is novel in that it inhibits the wild-type (wt) E1A protein from stimulating transcription from each of the early viral promoters E2, E3, and E4. Since both the hr5 and wt genes produced similar levels of E1A proteins, the ability of hr5 E1A to block transactivation was attributed to the replacement of serine by asparagine as position 185. We confirmed that this single amino acid substitution was responsible for blocking transactivation by showing equal inhibition with an hr5-wt hybrid E1A gene containing this missense mutation as the only alteration. The smaller 243R E1A protein of hr5 was not necessary for inhibition. Transcriptional activity from each early promoter was inhibited by at least 50% when the hr5 and wt E1A genes were present in equimolar amounts; complete inhibition occurred with a fivefold molar excess of the hr5 gene. Two other E1A missense mutant genes (hr3 and hr4) with amino acid substitutions in close proximity to that of hr5 failed to block wt E1A-induced transcription when similarly tested. Also, the hr5 E1A gene failed to impede the pseudorabies immediate early gene from transactivating the adenovirus E3 promoter, demonstrating that hr5 E1A inhibits wt E1A activation at the transcriptional, rather than the posttranscriptional, level. Although several possibilities were considered to account for this inhibition, the most likely is that the nonfunctional hr5 E1A protein competes with the wt 289R protein for a cellular transcription factor required for transactivation.

An adenovirus type 5 E1A protein with a single amino acid substitution blocks wild-type E1A transactivation

1987 ◽  
Vol 7 (3) ◽  
pp. 1004-1011
Author(s):  
G M Glenn ◽  
R P Ricciardi
Keyword(s):  
Amino Acid ◽  
Amino Acid Substitution ◽  
Adenovirus Type ◽  
Single Amino Acid Substitution ◽  
Single Amino Acid ◽  
Wild Type ◽  
Missense Mutant ◽  
E1a Gene ◽  
Adenovirus Type 5 ◽  
E1a Protein

The E1A gene of adenovirus type 5 encodes a 289-amino-acid (289R) protein that transactivates early adenovirus promoters. We showed that the 289R protein of the E1A missense mutant gene hr5 is novel in that it inhibits the wild-type (wt) E1A protein from stimulating transcription from each of the early viral promoters E2, E3, and E4. Since both the hr5 and wt genes produced similar levels of E1A proteins, the ability of hr5 E1A to block transactivation was attributed to the replacement of serine by asparagine as position 185. We confirmed that this single amino acid substitution was responsible for blocking transactivation by showing equal inhibition with an hr5-wt hybrid E1A gene containing this missense mutation as the only alteration. The smaller 243R E1A protein of hr5 was not necessary for inhibition. Transcriptional activity from each early promoter was inhibited by at least 50% when the hr5 and wt E1A genes were present in equimolar amounts; complete inhibition occurred with a fivefold molar excess of the hr5 gene. Two other E1A missense mutant genes (hr3 and hr4) with amino acid substitutions in close proximity to that of hr5 failed to block wt E1A-induced transcription when similarly tested. Also, the hr5 E1A gene failed to impede the pseudorabies immediate early gene from transactivating the adenovirus E3 promoter, demonstrating that hr5 E1A inhibits wt E1A activation at the transcriptional, rather than the posttranscriptional, level. Although several possibilities were considered to account for this inhibition, the most likely is that the nonfunctional hr5 E1A protein competes with the wt 289R protein for a cellular transcription factor required for transactivation.

scholarly journals A Single Amino Acid Substitution in the West Nile Virus Nonstructural Protein NS2A Disables Its Ability To Inhibit Alpha/Beta Interferon Induction and Attenuates Virus Virulence in Mice

2006 ◽  
Vol 80 (5) ◽  
pp. 2396-2404 ◽  
Author(s):  
Wen Jun Liu ◽  
Xiang Ju Wang ◽  
David C. Clark ◽  
Mario Lobigs ◽  
Roy A. Hall ◽  
...  
Keyword(s):  
West Nile Virus ◽  
Amino Acid ◽  
Amino Acid Substitution ◽  
Nonstructural Protein ◽  
Mutant Virus ◽  
Single Amino Acid Substitution ◽  
Single Amino Acid ◽  
Wild Type ◽  
Alpha Beta ◽  
A30p Mutation

ABSTRACT Alpha/beta interferons (IFN-α/β) are key mediators of the innate immune response against viral infection. The ability of viruses to circumvent IFN-α/β responses plays a crucial role in determining the outcome of infection. In a previous study using subgenomic replicons of the Kunjin subtype of West Nile virus (WNVKUN), we demonstrated that the nonstructural protein NS2A is a major inhibitor of IFN-β promoter-driven transcription and that a single amino acid substitution in NS2A (Ala30 to Pro [A30P]) dramatically reduced its inhibitory effect (W. J. Liu, H. B. Chen, X. J. Wang, H. Huang, and A. A. Khromykh, J. Virol. 78:12225-12235). Here we show that incorporation of the A30P mutation into the WNVKUN genome results in a mutant virus which elicits more rapid induction and higher levels of synthesis of IFN-α/β in infected human A549 cells than that detected following wild-type WNVKUN infection. Consequently, replication of the WNVKUNNS2A/A30P mutant virus in these cells known to be high producers of IFN-α/β was abortive. In contrast, both the mutant and the wild-type WNVKUN produced similar-size plaques and replicated with similar efficiency in BHK cells which are known to be deficient in IFN-α/β production. The mutant virus was highly attenuated in neuroinvasiveness and also attenuated in neurovirulence in 3-week-old mice. Surprisingly, the mutant virus was also partially attenuated in IFN-α/βγ receptor knockout mice, suggesting that the A30P mutation may also play a role in more efficient activation of other antiviral pathways in addition to the IFN response. Immunization of wild-type mice with the mutant virus resulted in induction of an antibody response of similar magnitude to that observed in mice immunized with wild-type WNVKUN and gave complete protection against challenge with a lethal dose of the highly virulent New York 99 strain of WNV. The results confirm and extend our previous original findings on the role of the flavivirus NS2A protein in inhibition of a host antiviral response and demonstrate that the targeted disabling of a viral mechanism for evading the IFN response can be applied to the development of live attenuated flavivirus vaccine candidates.

scholarly journals Analyses of Single-Amino-Acid Substitution Mutants of Adenovirus Type 5 E1B-55K Protein

2001 ◽  
Vol 75 (9) ◽  
pp. 4297-4307 ◽  
Author(s):  
Yuqiao Shen ◽  
Galila Kitzes ◽  
Julie A. Nye ◽  
Ali Fattaey ◽  
Terry Hermiston
Keyword(s):  
Gene Expression ◽  
Amino Acid ◽  
Human Cancer ◽  
Adenovirus Type ◽  
Single Amino Acid ◽  
Late Gene ◽  
Wild Type ◽  
Late Gene Expression ◽  
Human Cancer Cells ◽  
Adenovirus Type 5

ABSTRACT The E1B-55K protein plays an important role during human adenovirus type 5 productive infection. In the early phase of the viral infection, E1B-55K binds to and inactivates the tumor suppressor protein p53, allowing efficient replication of the virus. During the late phase of infection, E1B-55K is required for efficient nucleocytoplasmic transport and translation of late viral mRNAs, as well as for host cell shutoff. In an effort to separate the p53 binding and inactivation function and the late functions of the E1B-55K protein, we have generated 26 single-amino-acid mutations in the E1B-55K protein. These mutants were characterized for their ability to modulate the p53 level, interact with the E4orf6 protein, mediate viral late-gene expression, and support virus replication in human cancer cells. Of the 26 mutants, 24 can mediate p53 degradation as efficiently as the wild-type protein. Two mutants, R240A (ONYX-051) and H260A (ONYX-053), failed to degrade p53 in the infected cells. In vitro binding assays indicated that R240A and H260A bound p53 poorly compared to the wild-type protein. When interaction with another viral protein, E4orf6, was examined, H260A significantly lost its ability to bind E4orf6, while R240A was fully functional in this interaction. Another mutant, T255A, lost the ability to bind E4orf6, but unexpectedly, viral late-gene expression was not affected. This raised the possibility that the interaction between E1B-55K and E4orf6 was not required for efficient viral mRNA transport. Both R240A and H260A have retained, at least partially, the late functions of wild-type E1B-55K, as determined by the expression of viral late proteins, host cell shutoff, and lack of a cold-sensitive phenotype. Virus expressing R240A (ONYX-051) replicated very efficiently in human cancer cells, while virus expressing H260A (ONYX-053) was attenuated compared to wild-type virus dl309 but was more active than ONYX-015. The ability to separate the p53-inactivation activity and the late functions of E1B-55K raises the possibility of generating adenovirus variants that retain the tumor selectivity of ONYX-015 but can replicate more efficiently than ONYX-015 in a broad spectrum of cell types.

scholarly journals Conversion of NfsA, the Major Escherichia coliNitroreductase, to a Flavin Reductase with an Activity Similar to That of Frp, a Flavin Reductase in Vibrio harveyi, by a Single Amino Acid Substitution

1998 ◽  
Vol 180 (2) ◽  
pp. 422-425 ◽  
Author(s):  
Shuhei Zenno ◽  
Toshiro Kobori ◽  
Masaru Tanokura ◽  
Kaoru Saigo
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Hydrogen Bonds ◽  
Amino Acid Sequence ◽  
Amino Acid Substitution ◽  
Vibrio Harveyi ◽  
Single Amino Acid Substitution ◽  
Single Amino Acid ◽  
Flavin Reductase ◽  
Wild Type

ABSTRACT NfsA is the major oxygen-insensitive nitroreductase ofEscherichia coli, similar in amino acid sequence to Frp, a flavin reductase of Vibrio harveyi. Here, we show that a single amino acid substitution at position 99, which may destroy three hydrogen bonds in the putative active center, transforms NfsA from a nitroreductase into a flavin reductase that is as active as the authentic Frp and a tartrazine reductase that is 30-fold more active than wild-type NfsA.

scholarly journals Two “Wild-Type” Variants of Escherichia coli σ70: Context-Dependent Effects of the Identity of Amino Acid 149

2002 ◽  
Vol 184 (4) ◽  
pp. 1192-1195 ◽  
Author(s):  
Nicole E. Baldwin ◽  
Andrea McCracken ◽  
Alicia J. Dombroski
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Aspartic Acid ◽  
Amino Acid Substitution ◽  
Single Amino Acid Substitution ◽  
Single Amino Acid ◽  
Wild Type ◽  
Context Dependent

ABSTRACT The identity of amino acid 149 of Escherichia coli σ70 has been reported variably as either arginine or aspartic acid. We show that the behavior of both a region 1.2 deletion and a single-amino-acid substitution at position 122 are greatly affected by the identity of amino acid 149.

scholarly journals A large compressibility change of protein induced by a single amino acid substitution

1996 ◽  
Vol 5 (3) ◽  
pp. 542-545 ◽  
Author(s):  
Kunihiko Gekko ◽  
Youjiro Tamura ◽  
Eiji Ohmae ◽  
Hideyuki Hayashi ◽  
Hiroyuki Kagamiyama ◽  
...  
Keyword(s):  
Amino Acid ◽  
Amino Acid Substitution ◽  
Single Amino Acid Substitution ◽  
Single Amino Acid
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