instruction:
In this task, you're given a paragraph from the research paper and your task is to generate a suitable title for the research paper based on the given paper. Under 100 words is a good title length.
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The purpose of this study was to compare the biochemical and biological properties of nonstructural protein (nsp) 15 among mouse hepatitis virus (MHV), severe acute respiratory syndrome coronavirus (SARS-CoV) and transmissible gastroenteritis virus (TGEV) in virus-infected and ectopically expressed cells. In virus-infected cells, MHV nsp15 distributed unevenly throughout the cytoplasm but predominantly in the perinuclear region. When expressed as N-terminal enhanced green fluorescence protein (EGFP) fusion, it predominantly formed speckles in the cytoplasm. In contrast, SARS-CoV and TGEV EGFP-nsp15s distributed smoothly in the whole cell and did not form speckles. Deletion mapping experiments identified two domains responsible for the speckle formation in MHV EGFP-nsp15: Domain I (aa101-150) and Domain III (aa301-374). Interestingly, Domain II (aa151-250) had an inhibitory effect on Domain IIIbut not on Domain I-mediated speckle formation. Expression of a small (35aa) sequence in Domain III alone was sufficient to form speckles for all 3 viral nsp15s. However, addition of surrounding sequences in Domain III abolished the speckle formation for TGEV nsp15 but not for MHV and SARS-CoV nsp15s. Further domain swapping experiments uncovered additional speckle-inducing and -suppressive elements in nsp15s of SARS-CoV and TGEV. Homotypic interaction involving Domain III of MHV nsp15 was further demonstrated biochemically. Moreover, the biological functions of the expressed nsp15s were assessed in MHV-infected cells. It was found that the effects of EGFP-nsp15s on MHV replication were both virus species-and nsp15 domain-dependent. Collectively these results thus underscore the differential biochemical and biological functions among the nsp15s of MHV, TGEV and SARS-CoV in host cells.
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Comparative in vivo analysis of the nsp15 endoribonuclease of murine, porcine and severe acute respiratory syndrome coronaviruses

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Here we describe a novel endonuclease IV (Endo IV) based assay utilizing a substrate that mimics the abasic lesions that normally occur in doublestranded DNA. The three component substrate is characterized by single-stranded DNA target, an oligonucleotide probe, separated from a helper oligonucleotide by a one base gap. The oligonucleotide probe contains a non-fluorescent quencher at the 5 0 end and fluorophore attached to the 3 0 end through a special rigid linker. Fluorescence of the oligonucleotide probe is efficiently quenched by the interaction of terminal dye and quencher when not hybridized. Upon hybridization of the oligonucleotide probe and helper probe to their complementary target, the phosphodiester linkage between the rigid linker and the 3 0 end of the probe is efficiently cleaved, generating a fluorescent signal. In this study, the use of the Endo IV assay as a post-PCR amplification detection system is demonstrated. High sensitivity and specificity are illustrated using single nucleotide polymorphism detection.
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A novel endonuclease IV post-PCR genotyping system

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TABLE 40.1 Proposed Mechanisms of Virus-Induced CNS Demyelination CNS infection Infection of oligodendrocytes Direct destruction Pathogenic immune response to viral antigens on cell membranes Introduction of cell membranes into systematic circulation Infection of other CNS cells Release of cytokines or viral proteins toxic to myelin supporting cells or myelin membranes Extraneural infection Molecular mimicry (virus proteins and myelin proteins) Disruption of immune responses 954 40. INFECTIOUS DEMYELINATING DISEASES Definition ADEM is an acute, inXammatory, demyelinating disease of the brain and spinal cord. In most patients it has an abrupt onset days to several weeks after a viral exanthem or viruslike illness. But the disease is not speciWc to viruses and has been reported after several bacterial illnesses, immunizations, and drug and serum administration. The nosology is confusing, since the disease has been described under a remarkable variety of names. Post-infectious, parainfectious, post-exanthematous, post-vaccinal, postmeasles, and post-inXuenzal encephalomyelitis have been applied to describe the clinical settings. Acute disseminated encephalomyelitis, perivascular myelinoclasis, perivenous encephalitis, and acute demyelinating encephalomyelitis have been coined to describe the pathological features. Allergic encephalomyelitis, immune-mediated encephalomyelitis, hyperergic encephalomyelitis, and disseminated vasculomyelinopathy imply knowledge of pathogenetic mechanisms . Since the essential features for diagnosis are the neuropathological changes, ADEM will be used here except in speciWc cases such as post-measles and post-vaccinal encephalomyelitis. Acute hemorrhagic necrotizing leukoencephalits is generally regarded as a more intense, ''hyperacute'' form of ADEM. However, this rare acute demyelinating disease has distinct clinical and pathological features and is associated with a diVerent spectrum of antecedent infections. ADEM was a common disease in the mid-20th century, representing about one-third of all cases of encephalitis. The most common cause of ADEM was measles, which, along with ADEM cases following rubella and mumps, has been largely eliminated in regions of the world that have adequately protected children with the measles-mumps-rubella (MMR) vaccine. The second major cause of ADEM was a vaccine, vaccinia virus, which was discontinued after the worldwide eradication of natural smallpox in 1977. More recently, the varicella vaccine has further reduced the risk of ADEM. Now in countries with active childhood vaccination programs, ADEM makes up less than 10% of the cases of encephalitis, and the most common antecedent illnesses are nonspeciWc respiratory infections (Johnson, 1998) . The incidence of ADEM after clinically distinctive virus illnesses is highly variable (Tab. 40.2); the incidence after Epstein-Barr (EB) virus, Mycoplasma pneumoniae, inXuenza, and nonspeciWc upper respiratory infections are uncertain. The clinical Wndings after speciWc infections show some distinctive features, and the mortality and morbidity rates are quite diVerent. Despite the common pathology, the pathogenesis may vary. Most data on pathogenesis relate to post-measles encephalomyelitis. In acute fatal cases the brain may be congested and swollen. On gross sections, vessels are prominent in white matter with discoloration along the veins.
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Infectious Demyelinating Diseases