Planarian secretory cell nidovirus: The largest genome of RNA viruses

2021 ◽  
Author(s):  
Milad Zandi
Keyword(s):  
Secretory Cell ◽  
Rna Viruses

scholarly journals A planarian nidovirus expands the limits of RNA genome size

2018 ◽  
Author(s):  
Amir Saberi ◽  
Anastasia A. Gulyaeva ◽  
John L. Brubacher ◽  
Phillip A. Newmark ◽  
Alexander E. Gorbalenya
Keyword(s):  
Genome Size ◽  
Secretory Cell ◽  
Rna Viruses ◽  
Rna Virus ◽  
Evolutionary Analysis ◽  
Reading Frame ◽  
Autonomous Replication ◽  
Rna Genome ◽  
On The Road ◽  
Cellular Dna

AbstractRNA viruses are the only known RNA-protein (RNP) entities capable of autonomous replication (albeit within a permissive environment). A 33.5-kb nidovirus has been considered close to the upper size limit for such entities; conversely, the minimal cellular DNA genome is ~200 kb. This large difference presents a daunting gap for the transition from primordial RNP to contemporary DNA-RNP-based life. Whether or not RNA viruses represent transitional steps on the road to DNA-based life, studies of larger RNA viruses advance our understanding of size constraints on RNP entities. For example, emergence of the largest previously known RNA genomes (20-34 kb in positive-stranded nidoviruses, including coronaviruses) is associated with a proofreading exoribonuclease encoded in the nidoviral open reading frame 1b (ORF1b). However, apparent constraints on the size of ORF1b, which encodes this and other key replicative enzymes, have been hypothesized to limit further expansion of viral RNA genomes. Here, we characterize a novel nidovirus (planarian secretory cell nidovirus; PSCNV) whose disproportionately large ORF1b-like region, and overall 41.1 kb genome, substantially extend the presumed limits on RNA genome size. This genome encodes a predicted 13,556-aa polyprotein in an unconventional single ORF, yet retains canonical nidoviral genome organization and expression, and key replicative domains. Our evolutionary analysis suggests that PSCNV diverged early from multi-ORF nidoviruses, and subsequently acquired additional genes, including those typical of large DNA viruses or hosts. PSCNV’s greatly expanded genome, proteomic complexity, and unique features – impressive in themselves – attest to the likelihood of still-larger RNA genomes awaiting discovery.Significance StatementRNA viruses are the only known RNA-protein (RNP) entities capable of autonomous replication. The upper genome size for such entities was assumed to be <35 kb; conversely, the minimal cellular DNA genome is ~200 kb. This large difference presents a daunting gap for the proposed evolution of contemporary DNA-RNP-based life from primordial RNP entities. Here, we describe a nidovirus from planarians, whose 41.1 kb genome is 23% larger than the largest known of RNA virus. The planarian secretory cell nidovirus has broken apparent constraints on the size of the genomic subregion that encodes core replication machinery, and has acquired genes not previously observed in RNA viruses. This virus challenges and advances our understanding of the limits to RNA genome size.

Oncogenesis and the Lucké Virus

1968 ◽  
Vol 26 ◽  
pp. 200-201
Author(s):  
A. E. Vatter ◽  
J. Zambernard
Keyword(s):  
Rna Viruses ◽  
Vegetative State ◽  
Temperature Sensitive ◽  
Structural Level ◽  
Oncogenic Viruses ◽  
Dna Viruses ◽  
Leopard Frogs ◽  
Renal Adenocarcinoma ◽  
Induced Tumors ◽  
Northern Leopard Frogs

Oncogenic viruses, like viruses in general, can be divided into two classes, those that contain deoxyribonucleic acid (DNA) and those that contain ribonucleic acid (RNA). The RNA viruses have been recovered readily from the tumors which they cause whereas, the DNA-virus induced tumors have not yielded the virus. Since DNA viruses cannot be recovered, the bulk of present day investigations have been concerned with RNA viruses.The Lucké renal adenocarcinoma is a spontaneous tumor which occurs in northern leopard frogs (Rana pipiens) and has received increased attention in recent years because of its probable viral etiology. This hypothesis was first advanced by Lucké after he observed intranuclear inclusions in some of the tumor cells. Tumors with inclusions were examined at the fine structural level by Fawcett who showed that they contained immature and mature virus˗like particles.The use of this system in the study of oncogenic tumors offers several unique features, the virus has been shown to contain DNA and it can be recovered from the tumor, also, it is temperature sensitive. This latter feature is of importance because the virus can be transformed from a latent to a vegetative state by lowering or elevating the environmental temperature.

The Effects of Estradiol on Chronically Damaged Human Fallopian Tubes: A SEM Study

1985 ◽  
Vol 43 ◽  
pp. 648-649
Author(s):  
A. Toledo ◽  
G. Stoelk ◽  
M. Yussman ◽  
R.P. Apkarian
Keyword(s):  
Menstrual Cycle ◽  
Epithelial Cell ◽  
Secretory Cell ◽  
Estrogen Therapy ◽  
Fallopian Tubes ◽  
Cell Surfaces ◽  
Proliferative Phase ◽  
Cyclic Patterns ◽  
Sem Study ◽  
The U.S

Today it is estimated that one of every three women in the U.S. will have problems achieving pregnancy. 20-30% of these women will have some form of oviductal problems as the etiology of their infertility. Chronically damaged oviducts present problems with loss of both ciliary and microvillar epithelial cell surfaces. Estradiol is known to influence cyclic patterns in secretory cell microvilli and tubal ciliogenesis, The purpose of this study was to assess whether estrogen therapy could stimulate ciliogenesis in chronically damaged human fallopian tubes.Tissues from large hydrosalpinges were obtained from six women undergoing tuboplastic repair while in the early proliferative phase of fheir menstrual cycle. In each case the damaged tissue was rinsed in heparinized Ringers-lactate and quartered.

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