Search PubMed⌕ Search

Biomedical subjects

H Will

Publications and source records attributed to H Will.

At least 73 records · Page 4Linked to original sources
PubMed1997

Differentiation of core gene products of the hepatitis B virus in infected liver tissue using monoclonal antibodies.

Hepatitis B virus (HBV) core gene translational products were localised previously in the cytoplasm and/or in the nuclei of infected cells. We investigated in naturally infected human hepatocytes whether this variation in the subcellular expression is due to differences in the presence of assembled core particles and other core gene derived proteins, the expression of HBeAg and the processing of liver tissue. By immunostaining of liver specimens infected with HBeAg-positive and HBeAg-minus variants of HBV, using monoclonal antibodies specific for assembled core particles and for various epitopes on denatured core protein, it was shown that virtually all immunoreactive core gene products are assembled into core particles. The latter are present both in the nuclei and in the cytoplasm of hepatocytes, independent of the infecting virus strain. A marked reduction or absence of immunoreactivity, observed with some monoclonal antibodies, was shown to result from nucleotide sequence variations within or close to the corresponding epitope. These results demonstrate that immunoreactive products, derived from the HBV core gene, in the nuclei and cytoplasm of human hepatocytes represent assembled core particles and that monoclonal antibodies with known recognition sites can reveal region-specific core gene variation of the infecting HBV population.

Amino Acid Sequence↗
PubMed1997

Prevalence, kinetics, and therapeutic modulation of autoantibodies against Sp100 and promyelocytic leukemia protein in a large cohort of patients with primary biliary cirrhosis.

Antinuclear antibodies (ANA) staining nuclear dot structures predominantly occur in primary biliary cirrhosis (PBC) patients and recognize the Sp100 and promyelocytic leukemia protein (PML). From retrospective analysis of sera from a clinically well-defined Canadian series of 170 PBC patients included into a 24-month therapeutic trial of ursodeoxycholic acid (UDCA), we report the prevalence of these ANA and their dynamics in the course of the disease. Using an enzyme-linked immunosorbent assay (ELISA), anti-Sp100 autoantibodies were shown in 35 (21%) patients. Thirty-three patients (19%) had autoantibodies against PML as determined by indirect immunostaining of cells overexpressing PML. Altogether, anti-nuclear dot autoantibodies were present in 25% of the 170 PBC patients. Their occurrence correlated with an unfavorable disease course, because these patients progressed significantly more frequently from early stages (I/II) to late stages (III/IV) within the 24-month observation period (P < .05). During the course of the disease, the autoantibody levels against the Sp100 full-length protein remained nearly constant in all 35 positive patients. However, 9 patients showed remarkable changes in Sp100 epitope recognition as revealed by ELISA and immunoblotting. When the occurrence of these changes and the treatment of the patients were compared retrospectively, it became evident that 8 of the 9 patients had received UDCA (42% of all Sp100-positive patients treated with UDCA). These findings indicate subtle changes of the Sp100 epitope recognition pattern during the natural course of the disease and its induction or acceleration by UDCA treatment. This implies that UDCA can modulate immunoglobulin (Ig) expression not only quantitatively, but also qualitatively.

Adult↗
PubMed1997

Familial clustering of HBV pre-C and pre-S mutants.

BACKGROUND/AIMS: Little is known about the persistence and risk of infection with hepatitis B viruses (HBV) containing mutations in the pre-C and pre-S region. The aim of this study was to study the long-term persistence and the risk of intrafamilial spreading of these variants. METHODS: Serological markers were analyzed immunologically and pre-C and pre-S sequences of HBV DNA in sera from several members of five families by DNA amplification and direct sequencing. RESULTS: In most HBV-DNA positive individuals of each family, either the dominant HBV population or a subpopulation had a stop codon in the pre-C region which prevented expression of e-antigen. The pre-S region of the dominant virus populations of 8/15 HBV-DNA positive sera showed different deletions or a pre-S2 translation initiation codon mutation in addition to various point mutations. Selection for pre-C and pre-S mutant viruses from a predominant "wildtype" virus population was observed in three individuals during the natural course of infection. Persistence of a pre-C/pre-S double mutant virus as a stable strain for 6 years was found in one patient. CONCLUSIONS: These data indicate extensive intrafamilial clustering of HBV variants with mutations in the pre-C and pre-S regions due to patient-specific selection mechanisms and long-term persistence of some mutants as stable strains. The type of viruses found suggests that occasionally virus subpopulations are selectively transmitted or become a dominant virus population after selection.

Cluster Analysis↗
PubMed1997

Hepatitis B virus sequence changes evolving in liver transplant recipients with fulminant hepatitis.

BACKGROUND/AIMS: Patients undergoing liver transplantation for hepatitis B virus (HBV) related liver cirrhosis are at major risk of developing HBV recurrence, and occasionally fulminant hepatitis. Here we tested in a longitudinal study whether specific viral variants are associated with fulminant HBV infection in the graft. METHODS: The complete HBV genomes isolated from the sera of three patients with HBV and HBV and hepatitis delta virus (HDV) coinfection during chronic infection before and during fulminant reinfection after transplantation were amplified and directly sequenced. RESULTS: Twenty, 25 and 19 mutations, distributed over the entire genome, were identified which differed between the HBV genomes isolated from each patient during chronic and fulminant infection, respectively. This reflects a much higher rate of nucleotide sequence changes than expected from the natural variation of HBV. No common HBV mutation emerged in any of the three cases during fulminant infection. However, precore defective viruses were found to be present in all three patients at the time of fulminant infection and in two of the patients before fulminant infection. Two of the patients had preS2-defective HBVs both before and after transplantation. A point mutation in the 'a'-determinant of the surface protein emerged in one case after transplantation under treatment with polyclonal HBV specific immunoglobulins. CONCLUSIONS: Many new, but no specific common mutations emerged during fulminant HBV reinfection. Although HBeAg defective variants were found in all cases studied, the presence of these variants also during chronic infection in two cases demonstrates that they are not sufficient to cause fulminant hepatitis. Thus, other factors than the emergence of a specific viral strain seem to contribute to the development of fulminant reinfection in a liver graft.

Adult↗
PubMed1997

Nuclear dots: actors on many stages.

Nuclear dots (NDs), alternatively designated nuclear bodies (NBs), PML oncogenic domains (PODs), nuclear domain 10 (ND10) or Kr-bodies, became a major topic for researchers in many fields only recently. Originally described as an autoantigenic target in patients with primary biliary cirrhosis, they are now also known to play a role in development of acute promyelocytic leukemia (APL) and possibly other forms of neoplasia. Size, number and composition of NDs are regulated throughout the cell cycle. Infection with herpes simplex virus, adenovirus, cytomegalovirus, Epstein-Barr-virus, influenza virus and human T cell lymphotropic virus type I (HTLV I) strongly modifies ND structure through viral regulatory proteins. Due to this finding and because at least three of the cellular ND proteins are highly interferon-inducible, a function of NDs in early viral infection or in antiviral response has been postulated. Functional data are currently available only for two of the ND-associated proteins. The Sp100 protein seems to have transcriptional transactivating property, whereas the promyelocytic leukemia protein (PML) was reported to suppress growth and transformation. Here, we give a brief overview of the data currently available on NDs. Thus, we hope to link seemingly unrelated findings in the literature on oncology, virology, cell biology and immunology.

Animals↗
PubMed1997

Autoantibodies against "nuclear dots" in primary biliary cirrhosis.

Autoantibodies against nuclear proteins are not always but rather frequently present in sera of patients with primary biliary cirrhosis (PBC). The specificity and diagnostic value of these autoantibodies for PBC have only recently become clear through cloning of the cDNA of some of the corresponding autoantigens which allowed the establishment of immunological assays with recombinant autoantigens expressed in E. coli and eukaryotic cells. In this report we summarize primarily the knowledge on the structure and putative function of two nuclear autoantigens, the Sp100 and PML proteins, which are present in so-called nuclear dots (NDs) and against which autoantibodies are present in a subpopulation of PBC patients. Furthermore, the type of autoimmune response (epitope specificity and immunoglobulin class) against both the Sp100 and PML proteins and the specificity of the anti-Sp100 and anti-PML autoantibodies for PBC patients and patients with other autoimmune diseases is reviewed. Current knowledge clearly indicates that determination of anti-Sp100 and anti-PML autoantibodies substantially improves diagnosis of PBC as these autoantibodies are highly specific for this disease even when autoantibodies against mitochondrial antigens, a hallmark of most PBC patients, are not found. The type of autoimmune response against the Sp100 and PML proteins also provides some clues about possible mechanisms which lead to autoantigenicity of both proteins.

Antigens, Nuclear↗
PubMed1997

Sequence heterogeneity of heron hepatitis B virus genomes determined by full-length DNA amplification and direct sequencing reveals novel and unique features.

So far, only a single heron hepatitis B virus genome (HHBV-4) has been cloned and sequenced. Therefore, neither the significance of its sequence divergence from other avian hepadnaviruses nor the sequence variability of HHBV genomes in general are known. Here we have analysed the sequence heterogeneity of HHBV genome populations in several sera from naturally infected herons. A highly sensitive PCR method for full-length HHBV genome amplification was established which allowed direct sequencing of entire HHBV populations without prior cloning. Sequences of HHBV genomes from four sera were thus obtained which differed from those of HHBV-4 by up to 7%. Some of the divergent nucleotides and the corresponding amino acids of the predicted viral proteins were conserved in all four new HHBV isolates and varied only in HHBV-4. This indicates that the HHBV-4 genome is not in all aspects representative of this class of viruses. Interestingly, a highly conserved ORF upstream of the C-gene present in a position analogous to that of the mammalian hepadnavirus X-gene became apparent in all HHBV genomes. In contrast to the duck hepadnaviruses, the small (sAg-S) instead of the largest (sAg-L) envelope protein of all HHBVs has a myristylation site. These data confirm the significant sequence divergence of HHBV from other avian hepadnaviruses. Moreover, they show that HHBV has low sequence variability and indicate two new and unique features not evident in other avihepadnaviruses: an additional, highly conserved gene and potential myristylation of the sAg-S instead of the sAg-L envelope protein.

Amino Acid Sequence↗
PubMed1997

Activation of progelatinase A and progelatinase A/TIMP-2 complex by membrane type 2-matrix metalloproteinase.

C-terminal truncated membrane-type 2 matrix metalloproteinase (MT2-MMP1-269), comprising prodomain and catalytic domain, was expressed as a soluble protein in Escherichia coli. Unlike the corresponding form of MT1-MMP, which can be isolated as a 31 kDa protein, MT2-MMP1-269 proved to be comparatively instable, and already the freshly isolated preparation displayed several proteins in SDS-PAGE representing MT2-MMP1-269 (33 kDa) and four N-truncated forms with N-termini methionine32 (30 kDa), isoleucine37 (30 kDa), leucine84 (24 kDa), and leucine93 (22 kDa), the catalytic domain. After thawing of frozen preparations the 33 and the 30 kDa proforms were no longer detectable in SDS-PAGE, and only the 24 and 22 kDa forms remained. The catalytic domain of MT2-MMP activated progelatinase A as well as the progelatinase A/TMP-2 complex by cleaving the 72 kDa progelatinase A to yield 67 kDa gelatinase A, which is then transformed into 62 kDa gelatinase A. The 62 kDa form is about twice as active as the 67 kDa form towards the synthetic substrate N-(2,4)-dinitrophenyl-Pro-Gln-Gly-Ile-Ala-Gly-Gln-D-Arg. No significant difference in activity was found between free and complexed gelatinase A forms. the activation of the progelatinase A/TIMP-2 complex proceeds in two steps: At first MT2-MMP is inhibited by the progelatinase A/TIMP-2/MT2-MMP, complex, whereby a ternary complex, progelatinase A/TIMP-2/ MT-2MMP is generated. This ternary complex is then activated by excess MT2-MMP. Our results suggest a mechanism for spatially regulated extracellular gelatinase A activity mediated by activation with membrane-type MMPs; Free gelatinase A is released into the extracellular space, while gelatinase A/TIMP-2 bound to MT-MMP remains anchored on the cell surface.

Enzyme Activation↗
PubMed1996

The interferon (IFN)-stimulated gene Sp100 promoter contains an IFN-gamma activation site and an imperfect IFN-stimulated response element which mediate type I IFN inducibility.

Expression of the nuclear domain-associated proteins Sp100, PML, and NDP52, is enhanced by interferons (IFNs) on the mRNA and protein level. Increase both of Sp100 and PML mRNA is due to enhanced transcription of the corresponding genes which occurs independently of cellular protein synthesis immediately upon IFN-beta addition. Here, we describe the molecular cloning and functional analysis of the Sp100 promoter. DNA sequence analysis revealed potential binding sites for several constitutive and IFN-inducible transcription factors. Consistent with the absence of a TATA box and an initiator element, several transcription initiation sites were found. Transient expression studies identified an imperfect IFN-stimulated response element within the first 100 nucleotides upstream of the major transcription start site. This element rendered a heterologous promoter IFN-beta-inducible and bound IFN-stimulated gene factor 2 strongly but IFN-stimulated gene factor 3 only weakly. An IFN-gamma activation site approximately 500 base pairs upstream of the IFN-stimulated response element was found to bind three IFN-alpha/beta activation factors upon IFN-beta induction and conferred both type I and type II IFN inducibility upon a heterologous promoter. These data demonstrate a novel arrangement of a nonoverlapping IFN-gamma activation site and an IFN-stimulated response element mediating type I IFN inducibility, previously not reported for other IFN-stimulable promoters.

Antigens, Nuclear↗
PubMed1996

The soluble catalytic domain of membrane type 1 matrix metalloproteinase cleaves the propeptide of progelatinase A and initiates autoproteolytic activation. Regulation by TIMP-2 and TIMP-3.

It has been proposed that the cell-mediated activation of progelatinase A requires binding of the C-terminal domain of the proenzyme to a membrane-associated complex of the membrane type matrix metalloproteinase MT1-MMP and TIMP-2. Subsequent sequential proteolysis of the propeptide by MT1-MMP and gelatinase A is thought to generate the active form of gelatinase A. We have prepared the proform of the catalytic domain of the MT1-MMP and demonstrated that this may be activated in vitro by trypsin proteolysis to yield a functional proteinase capable of cleaving typical metalloproteinase peptide substrates, gelatin and casein. The active catalytic domain of MT1-MMP was also shown to activate progelatinase A to a fully active form. Using the inactive mutant pro-E375A gelatinase A, we dissected the propeptide processing events that occur. MT1-MMP cleaves the propeptide at the sequence Asn37-Leu38 only. Further cleavage of the mutant enzyme propeptide at Asn80-Tyr81, equivalent to that of the active wild type gelatinase A, could only be effected by addition of gelatinase A to the system. TIMP-1 was essentially unable to prevent MT1-MMP processing of wild type or E375A progelatinase A, whereas TIMP-2 and TIMP-3 were good inhibitors of these events. Analysis of the rate of binding of TIMPs to the catalytic domain of MT1-MMP using kinetic methods showed that TIMP-1 is an extremely poor inhibitor of MT1-MMP. In comparison, TIMP-2 and TIMP-3 are excellent inhibitors, binding more rapidly to the catalytic domain of MT1-MMP than to the catalytic domain of gelatinase A. These data demonstrate the basic mechanism of MT1-MMP action on progelatinase A and the reason for the lack of inhibition by TIMP-1 previously demonstrated in cell-based activation studies.

Amino Acid Sequence↗
PubMed1996

Cellular mechanisms for human procollagenase-3 (MMP-13) activation. Evidence that MT1-MMP (MMP-14) and gelatinase a (MMP-2) are able to generate active enzyme.

Gelatinase A and membrane-type metalloproteinase (MT1-MMP) were able to process human procollagenase-3 (Mr 60,000) to the fully active enzyme (Tyr85 N terminus; Mr 48,000). MT1-MMP activated procollagenase-3 via a Mr 56,000 intermediate (Ile36 N terminus) to 48,000 which was the result of the cleavage of the Glu84-Tyr85 peptide bond. We have established that the activation rate of procollagenase-3 by MT1-MMP was enhanced in the presence of progelatinase A, thereby demonstrating a unique new activation cascade consisting of three members of the matrix metalloproteinase family. In addition, procollagenase-3 can be activated by plasmin, which cleaved the Lys38-Glu39 and Arg76-Cys77 peptide bonds in the propeptide domain. Autoproteolysis then resulted in the release of the rest of the propeptide domain generating Tyr85 N-terminal active collagenase-3. However, plasmin cleaved the C-terminal domain of collagenase-3 which results in the loss of its collagenolytic activity. Concanavalin A-stimulated fibroblasts expressing MT1-MMP and fibroblast-derived plasma membranes were able to process human procollagenase-3 via a Mr 56,000 intermediate form to the final Mr 48,000 active enzyme which, by analogy with progelatinase A activation, may represent a model system for in vivo activation. Inhibition experiments using tissue inhibitor of metalloproteinases, plasminogen activator inhibitor-2, or aprotinin demonstrated that activation in the cellular model system was due to MT1-MMP/gelatinase A and excluded the participation of serine proteinases such as plasmin during procollagenase-3 activation. We have established that progelatinase A can considerably potentiate the activation rate of procollagenase-3 by crude plasma membrane preparations from concanavalin A-stimulated fibroblasts, thus confirming our results using purified progelatinase A and MT1-MMP. This new activation cascade may be significant in human breast cancer pathology, where all three enzymes have been implicated as playing important roles.

Amino Acid Sequence↗
PubMed1996

Interferon-modulated expression of genes encoding the nuclear-dot-associated proteins Sp100 and promyelocytic leukemia protein (PML).

Promyelocytic leukemia protein (PML) and Sp100 are transcription-regulatory proteins which colocalize in discrete nuclear dots and play a role in autoimmunity, oncogenesis and virus-host interaction. Interferons (IFNs) were shown previously to increase strongly the levels of Sp100 mRNA and protein. Here, we examined which mechanisms lead to upregulation of Sp100 gene expression and whether IFNs also increase expression of the promyelocytic leukemia (PML) gene. We found that both mRNA and protein levels of PML are also strongly upregulated by IFNs. In addition, new Sp100 and PML proteins were detected immunologically after IFN treatment of cells. Nuclear run-on analysis revealed protein-synthesis-independent, rapid IFN-enhanced transcription rates as well as synergistic activation of the Sp100 and PML genes by type-I and type-II IFNs. These data demonstrate that PML and Sp100 belong to the growing family of IFN-stimulated genes (ISGs) upregulated most likely by the transcription factor ISGF3, and indicate that IFNs also qualitatively alter the expression of these two genes.

Antigens, Nuclear↗
PubMed1996

Hepatitis B virus genomes of patients with fulminant hepatitis do not share a specific mutation.

The pathogenesis of fulminant hepatitis B virus (HBV) infection is not well understood. The aim of this study was to investigate whether there is an association between specific viral variants and a fulminant disease course. The entire HBV genomes from the serum of eight patients with fulminant HBV infection and one patient with fulminant hepatitis during reinfection after liver transplantation were investigated. After isolation and amplification of viral DNA by polymerase chain reaction (PCR), plus and minus strands were directly sequenced. Sequence data were analyzed by comparative sequence alignments with 35 and 2 complete HBV genome sequences from patients without and with fulminant hepatitis, respectively. Several point mutations were present in all regions of the genomes. Many nucleotide changes had never or rarely been found in the reported HBV isolates from patients without fulminant hepatitis. A distinct mutation present in all genomes was not identified. Clusters of rare and unique mutations were observed in the enhancer II core promoter region. Mutations previously suggested to be associated with fulminant HBV infection were not consistently found. A precore stop codon mutation at nucleotide position 1896 or an A-to-T mutation at nucleotide position 1762 and a G-to-A mutation at nucleotide position 1764 in the core promoter region were present in four and three cases, respectively. Fulminant HBV infection does not appear to be caused by a specific genomic mutation. However, various mutations clustering in the enhancer II core promoter region may contribute to a fulminant disease course.

Adult↗
PubMed1996

Accumulation and persistence of hepatitis B virus core gene deletion mutants in renal transplant patients are associated with end-stage liver disease.

In renal transplant recipients, chronic hepatitis B virus (HBV) infection often leads to cirrhosis and liver failure. In this study, we investigated whether or not in these patients viral variants would emerge despite immunosuppression, and whether they are associated with a specific course of liver disease. In a population of 552 renal transplant recipients hepatitis B 24 surface antigen (HBsAg)-positive patients were available for a 2-year follow-up. By polymerase chain reaction (PCR) and DNA sequencing, HBV genomes with deletions in the middle of the core gene (C-gene) were found in 9 out of the 24 patients. Seven of the 9 patients (group I) showed either persistent or increasing amounts of these variants; all patients had cirrhosis, and 5 died of end-stage liver disease. The viral variants emerged at least 1 year before liver failure. In 2 out of the 9 patients, the core deletion variants disappeared, and no further deterioration of the liver function was observed thereafter. In the remaining 15 patients (group II) without deletion mutants detected at any time, only 3 had cirrhosis (P < .001, group I vs. II), and none died (P < .001). Between both groups, there were no statistically significant differences in the other relevant variables that were examined. These results indicate that HBV C-gene deletion mutants can accumulate in long-term immunosuppressed patients, and that their persistence is associated with progressive liver disease. The accumulation of these variants may be caused by the development of cirrhosis or could be involved in hepatopathogenesis.

Base Sequence↗
PubMed1996

Hepatitis B virus variants with core gene deletions in the evolution of chronic hepatitis B infection.

BACKGROUND & AIMS: Genomic variants of the hepatitis B virus (HBV) with core gene deletions have been identified in patients with chronic active hepatitis B, but the significance of these mutations in the course of chronic HBV infection remains unknown. The aim of this study was to longitudinally analyze the changes of HBV core gene deletion variants under the enhanced immune pressure of interferon alfa treatment and hepatitis B e antigen (HBeAg) to antibody to hepatitis B e antigen (anti-HBe) seroconversion. METHODS: HBV precore/core gene was amplified in 358 serum samples from 67 chronic HBV carriers (all HBeAg-positive) followed up for a period of 2-11 years. The core gene deletions were analyzed by gel electrophoresis, cloning, and DNA sequencing. RESULTS: HBV mutants with core gene deletions (37-250 base pairs) were detected in patients with long-standing HBV replication and ongoing hepatic inflammation, always together with the wild-type strain. They were associated with a significantly lower level of viremia and a high rate of seroconversion to anti-HBe. Core gene deletion mutants were preferentially eliminated after seroconversion, in contrast to the accumulation of HBV strains with a precore stop codon. CONCLUSIONS: These data indicate that HBV variants with core gene deletions may inhibit HBV replication, do not persist in preference of the wild-type HBV under enhanced immune pressure, and do not confer resistance to interferon alfa treatment.

Adult↗
PubMed1996

Type, prevalence, and significance of core promoter/enhancer II mutations in hepatitis B viruses from immunosuppressed patients with severe liver disease.

Little is known about the functional significance of hepatitis B virus (HBV) sequence heterogeneity. Here we analyzed the type, frequency, and function of mutations in the core promoter/enhancer II region of HBV in immunosuppressed patients. The major HBV population in immunosuppressed patients with severe liver disease had deletions, insertions, and/or base changes in this region. Such mutations were not found in immunosuppressed patients with mild disease. Except for two mutations, all created a hepatocyte nuclear factor 1 (HNF1) binding site or a potential HNF3 binding site. Occasionally, known binding sites for C/EBP and HNF4 were additionally duplicated. Eleven mutated core promoter prototype sequences were functionally tested in the context of a wild-type genome by transfection in Huh7 cells. Despite the diversity of mutations tested, all decreased steady-state levels of pre-C mRNA drastically and increased those of the C mRNA/ pregenomic RNA. This correlated with reduced levels of secreted hepatitis B e antigen and increased intracellular levels of core and Pol proteins and replicative HBV DNA intermediates. The levels of secreted HBV DNA-containing particles were also increased although most of the mutations reduced the levels of pre-S/S mRNA and pre-S1, and pre-S2 proteins as well as secretion of hepatitis B surface antigen. These data reveal a novel class of HBV variants with HNF1 binding sites in the core promoter which are characterized by a defect in hepatitis B e antigen expression, enhanced replication, and altered protein levels, all probably mediated by altered transcription factor binding. The phenotype of these variants and their prevalence only in immunosuppressed patients with severe liver disease may indicate that they play a role in pathogenesis.

Amino Acid Sequence↗
PubMed1996

A highly amplified mouse gene is homologous to the human interferon-responsive Sp100 gene encoding an autoantigen associated with nuclear dots.

In human cells, three proteins are currently known to colocalize in di screte nuclear domains (designated nuclear dots): Sp100, a transcription-activating protein autoantigenic primarily in patients with primary biliary cirrhosis; PML, a tumor suppressor protein involved in development of acute promyelocytic leukemia; and NDP52, a protein of unknown function. Here we report sequence similarities between the Sp100 protein and a putative protein encoded by a highly amplified mouse gene which is visible as an inherited homogeneously staining region (HSR) on chromosome 1 of some mouse populations. By in situ hybridization, the Sp100 gene was mapped to locus 2q37, the syntenic region of the HSR on mouse chromosome 1. Unlike the highly amplified mouse gene, Sp100 was found to be a single-copy gene and showed no restriction fragment length polymorphisms. Sequence similarities in the promoter regions and similar exon-intron organizations of the two genes were revealed. As for Sp100, steady-state levels of the mRNAs of the HSR-encoded genes could be greatly increased by interferon (IFN) treatment. As in human cells, IFN treatment led to an enlargement in both size and number of nuclear dots in mouse cells as visualized by immunofluorescence staining with autoimmune sera from patients with primary biliary cirrhosis. These data indicate that a gene located in the inherited HSR of mice, designated mSp100, is homologous to the human Sp100 gene, has a similar gene organization, and responds similarly to IFN treatment.

3T3 Cells↗