Life expectancy of young adults with follicular lymphoma.

BACKGROUND: This study was aimed at investigating the clinical features and outcomes of follicular lymphoma (FL) patients younger than 40 years, which have not been extensively investigated yet. PATIENTS AND METHODS: One hundred and fifty-five patients younger than 40 years were retrospectively studied from a series of 1002 FL patients diagnosed in four different European Oncology Centres (Barcelona, Spain; Bellinzona, Switzerland; London, UK; Novara, Italy) from 1985 to 2010. RESULTS: Patients younger than 40 had a lower incidence of elevated LDH, high beta2-microglobulin, and a high-risk Follicular Lymphoma International Prognostic Index (FLIPI) score, whereas bone marrow involvement and bulky and disseminated lymphadenopathy were more frequent. At a median follow-up of 10 years, younger patients, in comparison with those older than 40, had significantly better overall (OS), cause-specific survival (CSS), and progression-free survival (PFS), with 10-year OS rate of 81% versus 51% (P < 0.0001), 10-year CSS rate of 82% versus 60% (P < 0.0001), and 10-year PFS of 39% versus 24% (P = 0.0098). However, there were no significant CSS and PFS differences in comparison with the patients aged 40-60. In multivariate analysis, having the lymphoma diagnosed in the last two decades and a favourable FLIPI score were associated with a significantly longer PFS and CSS in younger patients, whereas only FLIPI retained statistical significance for OS. CONCLUSIONS: In our series, FL patients younger than 40 have a median OS of 24 years and their outcome seems to be improving over time. However, they still have a significantly shorter life expectancy than that of an age-matched general healthy population.

Histologic transformation in marginal zone lymphomas†.

BACKGROUND: Histologic transformation (HT) is a poorly understood event in patients with marginal zone lymphoma (MZL). The aim of this study was to analyze incidence and risk factors for HT in a large series of MZL patients. PATIENTS AND METHODS: The studied cohort included 340 MZL patients diagnosed and treated between 1995 and 2012: 157 extranodal MZLs [mucosa-associated lymphoid tissue (MALT) lymphoma, 46%], 85 splenic MZLs (SMZLs, 25%) and 37 nodal MZLs (NMZLs, 11%). Sixty-one patients (18%) had bone marrow infiltration at presentation, with or without detectable involvement of peripheral blood, but without other involved sites; they were considered clonal B-cell lymphocytosis of marginal zone origin (CBL-MZ). RESULTS: With a median follow-up of 4.8 years, the median overall survival and progression-free survival of the whole population were 14.5 and 5 years, respectively. HT was observed in 13 cases [3.8%, 95% confidence interval (95% CI) 2%-6.5%]. Elevated lactate dehydrogenase (LDH) at diagnosis was associated with the risk of HT (P = 0.019). HT occurred in 5% of SMZLs, 4% of MALT lymphomas, 3% of NMZLs and 3% of CBL-MZ (P = 0.974). The risk of HT was 5% (95% CI 3-9%) at 5 and 10 years after diagnosis and 10% (95% CI 5%-20%) at 12 years. At the time of HT, most patients had high LDH and B symptoms. At a median follow-up of 12 months after HT, 4 of 13 patients died, all for lymphoma-related causes, with a 2-year post-transformation survival rate of 57% (95% CI 13%-86%). CONCLUSIONS: In this large retrospective series, the risk of HT across all MZL types appeared lower than the one reported for follicular lymphoma.

Clinical activity of bortezomib in relapsed/refractory MALT lymphomas: results of a phase II study of the International Extranodal Lymphoma Study Group (IELSG).

BACKGROUND: The nuclear factor-kappa B activation in mucosa-associated lymphoid tissue (MALT) lymphoma pathogenesis provided the rationale for the evaluation of bortezomib in this malignancy. PATIENTS AND METHODS: Thirty-two patients with relapsed/refractory MALT lymphoma were enrolled. Thirty-one patients received bortezomib 1.3 mg/m(2) i.v., on days 1, 4, 8, and 11, for up to six 21-day cycles. RESULTS: Median age was 63 years (range, 37-82 years). Median number of prior therapies was 2 (range, 1-4). Nine patients had Ann Arbor stage I, 7 patients had stage II, and 16 patients had stage IV. Primary lymphoma localization was the stomach in 14 patients; multiple extranodal sites were present in 10 patients. Among the 29 patients assessable for response, the overall response rate was 48% [95% confidence interval (CI) 29% to 67%], with 9 complete and 5 partial responses. Nine patients experienced stable disease and six had disease progression during therapy. The most relevant adverse events were fatigue, thrombocytopenia, neutropenia, and peripheral neuropathy. After a median follow-up of 24 months, the median duration of response was not reached yet. Five deaths were reported, in two patients due to disease progression. CONCLUSION: Bortezomib is active in relapsed MALT lymphomas. Further investigations to identify optimal bortezomib dose, schedule, and combination regimens are needed since the frequent detection of dose-limiting peripheral neuropathy.

Modulation of DNA damage and DNA repair in chromatin.

DNA is packaged in the highly compact and dynamic structure of chromatin in eukaryotic cells. It is generally accepted that DNA processing events in the nucleus, such as transcription, replication, recombination, and repair, are restricted by this packaging. For some processes (e.g., transcription), the chromatin fiber is "preset" in a more open structure to allow access of proteins to specific regions of DNA within this structural hierarchy. These regions contain modified nucleosomes that accommodate a less compact state of chromatin and allow access to specific regions of DNA. DNA repair proteins, however, must access DNA lesions in all structural domains of chromatin after sudden insult to the genome. Damaged DNA must be recognized, removed, and replaced by repair enzymes at all levels of chromatin packaging. Therefore, the modulation of DNA damage and its repair in chromatin is crucial to our understanding of the fate of potential mutagenic and carcinogenic lesions in DNA. In this review, we discuss the modulation of DNA damage and DNA repair by chromatin structure, and the modulation of chromatin structure by these events.

Patterns of outcome and prognostic factors in primary large-cell lymphoma of the testis in a survey by the International Extranodal Lymphoma Study Group.

PURPOSE: To determine clinical features and patterns of outcome of primary testicular diffuse large B-cell lymphomas (DLCL). PATIENTS AND METHODS: A retrospective international survey of 373 patients with primary testicular DLCL. RESULTS: Most patients presented with localized disease (stage I to II), and the median age at diagnosis was 66 years (range, 19 to 91 years). Anthracycline-based chemotherapy was administered to 255 patients (68%), and prophylactic intrathecal chemotherapy was given to 68 patients (18%); 133 patients (36%) received prophylactic scrotal radiotherapy. Median overall survival was 4.8 years, and median progression-free survival was 4 years. The survival curves showed no clear evidence of a substantial proportion of cured patients. A favorable international prognostic index score (IPI), no B-symptoms, the use of anthracyclines, and prophylactic scrotal radiotherapy were significantly associated with longer survival at multivariate analysis. However, even for patients with stage I disease and good-risk IPI, the outcome seems worse than what was reported for DLCL at other sites. At a median follow-up of 7.6 years, 195 patients (52%) had relapsed. Extranodal recurrence was reported in 140 cases. Relapses in CNS were detected in 56 patients (15%) up to 10 years after presentation. A continuous risk of recurrence in the contralateral testis was seen in patients not receiving scrotal radiotherapy. CONCLUSION: Testicular DLCL is characterized by a particularly high risk of extranodal relapse even in cases with localized disease at diagnosis. Anthracycline-based chemotherapy, CNS prophylaxis, and contralateral testicular irradiation seem to improve the outcome. Their efficacy is under evaluation in a prospective clinical trial.

Psoralen-crosslinking of soluble and of H1-depleted soluble rat liver chromatin.

We purified soluble rat liver chromatin and H1-depleted chromatin and photocrosslinked its DNA with psoralen at pH 7. Digestion of this chromatin with micrococcal nuclease produced a normal nucleosomal repeat. Chromatin was photoreacted in the presence of 0 to 700 mM-NaCl and was fractionated in sucrose gradients containing the same NaCl concentrations. The dissociation of H1 occurred as in the non-crosslinked controls and no preferential dissociation of core histones was observed. The samples between 100 and 500 mM-NaCl showed precipitation. In the electron microscope, the fibers appeared indistinguishable from the controls at low ionic strength. In the presence of 40 mM-NaCl, the fibers of the photoreacted chromatin were slightly more compact than the controls, and at 500 mM-NaCl, despite the complete dissociation of H1, there were still apparently intact fibers at this ionic strength. The disruption of the psoralen-treated chromatin fibers occurred only in 600 mM-NaCl, as opposed to 500 mM-NaCl in controls. The DNA of all the photoreacted samples was spread for electron microscopy under denaturing conditions. They revealed, for all the samples, single-stranded bubbles corresponding to 200 to 400 base-pairs in size. H1-depleted chromatin containing stoichiometric amounts of core histones was photoreacted at pH 10 and very low ionic strength. Under these conditions many of the nucleosomes appeared to be unraveled, although to a variable extent. In the electron microscope, the purified DNA from these samples showed extensive crosslinking when spread under denaturing conditions. These observations show that histone-DNA interactions different from those in intact nucleosomes may be created, which allow extensive access of psoralen to the DNA.

Salicylic Acid Inhibits Synthesis of Proteinase Inhibitors in Tomato Leaves Induced by Systemin and Jasmonic Acid.

Salicylic acid (SA) and acetylsalicylic acid (ASA), previously shown to inhibit proteinase inhibitor synthesis induced by wounding, oligouronides (H.M. Doherty, R.R. Selvendran, D.J. Bowles [1988] Physiol Mol Plant Pathol 33: 377-384), and linolenic acid (H. Pena-Cortes, T. Albrecht, S. Prat, E.W. Weiler, L. Willmitzer [1993] Planta 191: 123-128), are shown here to be potent inhibitors of systemin-induced and jasmonic acid (JA)-induced synthesis of proteinase inhibitor mRNAs and proteins. The inhibition by SA and ASA of proteinase inhibitor synthesis induced by systemin and JA, as well as by wounding and oligosaccharide elicitors, provides further evidence that both oligosaccharide and polypeptide inducer molecules utilize the octadecanoid pathway to signal the activation of proteinase inhibitor genes. Tomato (Lycopersicon esculentum) leaves were pulse labeled with [35S]methionine, followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the inhibitory effects of SA are shown to be specific for the synthesis of a small number of JA-inducible proteins that includes the proteinase inhibitors. Previous results have shown that SA inhibits the conversion of 13S-hydroperoxy linolenic acid to 12-oxo-phytodienoic acid, thereby inhibiting the signaling pathway by blocking synthesis of JA. Here we report that the inhibition of synthesis of proteinase inhibitor proteins and mRNAs by SA in both light and darkness also occurs at a step in the signal transduction pathway, after JA synthesis but preceding transcription of the inhibitor genes.

Intracellular Levels of Free Linolenic and Linoleic Acids Increase in Tomato Leaves in Response to Wounding.

An intracellular signaling pathway for activating plant defense genes against attacking herbivores and pathogens is mediated by a lipid-based signal transduction cascade. In this pathway, linolenic acid (18:3) is proposed to be liberated from cell membranes and is converted to cyclopentanones that are involved in transcriptional regulation of defense genes, analogously to prostaglandin synthesis and function in animals. Levels of 18:3 and linoleic acid in tomato (Lycopersicon esculentum) leaves increased within 1 h when the leaves were wounded with a hemostat across the main vein to simulate herbivore attacks. The increase correlated with the time course of accumulation of jasmonic acid, a cyclopentanone product of 18:3, that had previously been shown to increase in leaves in response both to wounding and to elicitors of plant defense genes. One hour after wounding, at least a 15-fold excess of 18:3 was found over that required to account for the levels of newly synthesized jasmonic acid. The free fatty acids in both control and wounded leaves accounted for less than 0.25% of the total fatty acids. However, the total lipid contents of the leaves remained relatively unchanged up to 8 h after wounding, indicating that extensive loss of lipids did not occur, although a gradual decrease in polar lipids was observed, mainly in monogalactosyl diacylglycerol of chloroplast lipids. The data support a role for lipid release as a key step in the signaling events that activate defense genes in tomato leaves in response to wounding by attacking herbivores.

Lack of CD95/FAS gene somatic mutations in extranodal, nodal and splenic marginal zone B cell lymphomas.

Germline CD95 (also known as FAS, APT1 and APO1) gene mutations have been associated with benign lymphoproliferative diseases and autoimmune processes. Somatic mutations have been reported in human tumours, including lymphomas. Since marginal zone B cell lymphomas usually arise in a background of chronic inflammation, often of autoimmune origin, we searched for CD95 gene mutations in an unselected series of marginal zone B cell lymphomas. The CD95/FAS full coding region, comprising exon-intron junctions, was amplified from genomic DNA by polymerase chain reaction (PCR) in 10 separate reactions. PCR products were analysed by single-strand conformation polymorphism (SSCP) and visualised by silver staining. Bands exhibiting an altered electrophoretic mobility were sequenced. Twenty-seven cases of marginal zone B cell lymphomas of whom fresh or frozen tumour material was available (18 extranodal, five splenic and four nodal) were studied. Previously described silent polymorphisms in exons 7 (C836T) and 3 (T416C) were detected in 42% and in 19% of the cases, respectively. One silent T-to-A substitution at bp 431, within exon 3, was found in one case. Our results did not reveal the presence of CD95 somatic mutations in unselected cases of marginal zone B cell lymphomas. On the basis of our data, we cannot rule out that other genes coding for proteins involved in the CD95-induced apoptotic pathway might be altered. However, this pathway does not seem to play an important role in the pathogenesis of these lymphoma subtypes.

ACOD, a modified CHOP regimen for elderly patients with aggressive non-Hodgkin's lymphoma.

The aim of this study is to verify the feasibility and the clinical activity of a new CHOP-like schedule (ACOD) with a fractionated days 1 and 8 administration in elderly patients. This regimen was chosen in the attempt to allow a sufficient dose intensity (DI) of each drug with better compliance. Fifty-two patients, (74 years, median age), with diffuse large B cell non-Hodgkin's lymphoma were retrospectively evaluated. Patients received ADM 25 mg/sqm, CTX 500 mg/sqm, VCR 1.2 mg/sqm (max 2 mg intravenously) days 1 and 8 and PDN 50 mg orally, days 1-8. Results showed that 54% of patients reached a complete remission, 21% a partial remission with an overall response rate of 75%. Two-thirds of the patients received at least 70% of the planned dose of cyclophosphamide and doxorubicin and 50% of vincristine and prednisone. The median duration of follow up was 12.6 months (range 0.7-61.4). The estimated median OS was 15.2 months (95%CI = [11.6, not estimable]); the estimated median PFS was 5.7 months (95%CI = [5.12, not estimable]). After 2 years, the proportion of patients alive was 47% (95%CI = 34-64%) and the proportion of patients free from progression was 39% (95%CI = 27-57%). Grade 3-4 leukopenia was observed in 61% of patients with 11% of febrile neutropenia. In conclusion, the ACOD chemotherapy regimen seems safe and feasible in elderly patients. This schedule allowed a sufficient DI of chemotherapic agents with clinical results very similar to those recorded with the standard CHOP regimen in young adults.

Improved method for measuring the ensemble average of strand breaks in genomic DNA.

The cis-syn cyclobutane pyrimidine dimer (CPD) is the major photoproduct induced in DNA by low wavelength ultraviolet radiation. An improved method was developed to detect CPD formation and removal in genomic DNA that avoids the problems encountered with the standard method of endonuclease detection of these photoproducts. Since CPD-specific endonucleases make single-strand cuts at CPD sites, quantification of the frequency of CPDs in DNA is usually done by denaturing gel electrophoresis. The standard method of ethidium bromide staining and gel photography requires more than 10 microg of DNA per gel lane, and correction of the photographic signal for the nonlinear film response. To simplify this procedure, a standard Southern blot protocol, coupled with phosphorimage analysis, was developed. This method uses random hybridization probes to detect genomic sequences with minimal sequence bias. Because of the vast linearity range of phosphorimage detection, scans of the signal profiles for the heterogeneous population of DNA fragments can be integrated directly to determine the number-average size of the population.

Molecular detection of circulating neoplastic cells in patients with clinically localised gastric and non-gastric mucosa-associated lymphoid tissue lymphoma.

BACKGROUND: Unlike other low-grade lymphomas, extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue type usually presents with localised disease. AIM: To detect peripheral blood lymphoma involvement to establish the incidence of occult lymphoma dissemination. PATIENTS AND METHODS: In a series of 18 cases, peripheral blood was analysed by polymerase chain reaction, with primers directed to the third-complementarity determining region of the immunoglobulin heavy chain gene. RESULTS AND CONCLUSION: The presence of circulating neoplastic cells was detected in 21% of clinically localised cases. Moreover lymphoma cells were detected in 2 out of 6 morphologically normal bone marrow specimens. The present data show that, combining morphological and molecular methods, occult dissemination can be found in a large proportion of cases thus stressing the need for careful staging procedures. However, it has still to be clarified whether the presence of polymerase chain reaction-detectable circulating lymphoma cells can influence the outcome of mucosa-associated lymphoid tissue lymphoma patients submitted to antibiotic treatment (for gastric localisation) or local therapy (surgery or radiation, for non-gastric tumours).

Mitotic viability and metabolic competence in UV-irradiated yeast cells.

Colony formation is the classic method for measuring survival of yeast cells. This method measures mitotic viability and can underestimate the fraction of cells capable of carrying out other DNA processing events. Here, we report an alternative method, based on cell metabolism, to determine the fraction of surviving cells after ultraviolet (UV) irradiation. The reduction of 2,3,5-triphenyl tetrazolium chloride (or TTC) to formazan in mitochondria was compared with cell colony formation and DNA repair capacity in wt cells and two repair-deficient strains (rad1Delta and rad7Delta). Both TTC reduction and cell colony formation gave a linear response with different ratios of mitotically viable cells and heat-inactivated cells. However, monitoring the formation of formazan in non-dividing yeast cells that are partially (rad7Delta) or totally (wt) proficient at DNA repair is a more accurate measure of cell survival after UV irradiation. Before repair of UV photoproducts (cis-syn cyclobutane pyrimidine dimers or CPDs) is complete, these two assays give very different results, implying that many damaged cells are metabolically competent but cannot replicate. For example, only 25% of the rad7Delta cells are mitotically viable after a UV dose of 12 J/m(2)75% of these cells are metabolically competent and remove over 55% of the CPDs from their genomic DNA. Moreover, repair of CPDs in wt cells dramatically decreases after the first few hours of liquid holding (L.H.; incubation in water) and correlates with a substantial decrease in cell metabolism over the same time period. In contrast, cell colony formation may be the more accurate indicator of cell survival after UV irradiation of rad1Delta cells (i.e., cells with little DNA repair activity). These results indicate that the metabolic competence of UV-irradiated, non-dividing yeast cells is a much better indicator of cell survival than mitotic viability in partially (or totally) repair proficient yeast cultures.

Molecular characterization of common variable immunodeficiency-related lymphomas.

Common variable immunodeficiency (CVI) patients are at high relative risk of developing non-Hodgkin lymphomas (NHL), mainly represented by B-lineage diffuse large cell lymphomas. The molecular pathogenesis and histogenesis of CVI-related NHL are poorly understood. We have thus attempted to provide a detailed molecular characterization of their histogenesis and pathogenesis. A panel of 5 CVI-related NHL was subjected to detailed analysis of histogenetic markers (mutations of immunoglobulin variable heavy chain-IgVH and of BCL-6 genes) acquired by B-cells at the time of germinal center transit. Somatic hypermutation of IgVH and BCL-6 genes occurred in 5/5 cases; in all cases, mutations were stable with no evidence of ongoing mutation processes. In 3/5 cases, the pattern of IgVH mutations was consistent with selection and stimulation of the tumor clone by antigen. To further clarify the pathogenesis, samples were tested for inactivation by promoter hypermethylation of the genes 0(6)-methylguanine-DNA-methyltransferase (MGMT) and glutathione S-transferase (GST) p1, which code for detoxifying enzymes, as well as of death-associated protein (DAP)-kinase, coding for a proapoptotic molecule. Promoter hypermethylation of MGMT, GSTp1 and DAP-kinase was detected in 2/5, 3/5 and 3/5 CVI-related NHL, respectively. Overall, these data indicate that: i) similarly to other immunodeficiency-related NHL, CVI-related NHL derive from germinal center-related B-cells, namely centrocytes or post-germinal center B-cells; ii) antigen stimulation and selection are involved in the development of at least a fraction of these cases; iii) hypermethylation of the MGMT, DAP-kinase and GSTp1 genes occurs at sustained frequencies in CVI-related NHL and may provide novel prognostic markers and therapeutic targets for the clinical management of these lymphomas.

Progressive multifocal leucoencephalopathy after autologous bone marrow transplantation: a treatment option.

A patient with multiple myeloma was treated with high-dose chemotherapy followed by two autologous bone marrow transplantations (ABMTs). Nine months after the second ABMT the patient complained of severe left hemiparesis, paraesthesias, left homonymous visual field defects and gait ataxia. She was diagnosed with progressive multifocal leucoencephalopathy (PML) confirmed by detection of JC virus (JCV) DNA and prescribed cidofovir every other week and mirtazapine daily. Her symptoms and signs remained stable and after 6 months the JCV DNA was undetectable in the cerebrospinal fluid. Repeated MRI scans demonstrated the stabilisation of demyelinating lesion volume; after more than 2 years of follow-up the patient's neurological examination does not show significant variations. Combination of cidofovir and mirtazapine may be helpful in the treatment of PML in HIV-negative patients.

Analysis of the host pharmacogenetic background for prediction of outcome and toxicity in diffuse large B-cell lymphoma treated with R-CHOP21.

Knowledge on the impact of pharmacogenetics in predicting outcome and toxicity in diffuse large B-cell lymphoma (DLBCL) is scant. We tested 106 consecutive DLBCL treated with R-CHOP21 for 19 single nucleotide polymorphisms (SNPs) from 15 genes potentially relevant to rituximab-CHOP (R-CHOP) pharmacogenetics. Associations of SNPs with event-free survival (EFS) and toxicity were controlled for multiple testing. Genotypic variants of nicotinamide adenine dinucleotide phosphate (NAD(P)H) oxidase p22phox (CYBA rs4673) and alpha1 class glutathione S-transferase (GSTA1 rs3957357) were independent predictors of EFS (CYBA rs4673 TT genotype: HR 2.06, P=0.038; GSTA1 rs3957357 CT/TT genotypes: HR 0.38, P=0.003), after adjusting for International Prognostic Index (IPI). CYBA rs4673 and GSTA1 rs3957357 also predicted outcome in DLBCL subgroups by IPI. Impact of SNPs on toxicity was evaluated in 658 R-CHOP21 courses utilizing generalized estimating equations. NCF4 rs1883112 was an independent predictor against hematologic (odds ratios (OR): 0.45; P=0.018), infectious (OR: 0.46; P=0.003) and cardiac toxicity (OR: 0.37; P=0.023). Overall, host SNPs affecting doxorubicin pharmacodynamics (CYBA rs4673) and alkylator detoxification (GSTA1 rs3957357) may predict outcome in R-CHOP21-treated DLBCL. Also, NCF4 rs1883112, a SNP of NAD(P)H oxidase p40phox, may have a function in protecting against hematologic and nonhematologic toxicity. These results highlight the need to improve characterization of the host genetic background for a better prognostication of DLBCL.

Reactive perivascular T-cell infiltrate predicts survival in primary central nervous system B-cell lymphomas.

Well-established histopathological prognostic factors are lacking in primary central nervous system (CNS) lymphomas (PCNSL). The present study investigated the presence and prognostic role of tumour necrosis (TN) and reactive perivascular T-cell infiltrate (RPVI), defined as a rim of small reactive T-lymphocytes occurring alone or located between the vascular wall and large neoplastic cells, in tumour samples from 100 immunocompetent patients with PCNSL. World Health Organization histotypes of the patients were: 96 diffuse large B-cell lymphomas, two Burkitt-like lymphomas, one anaplastic large T-cell lymphoma and one unclassified B-cell lymphoma. TN was observed in 24 (24%) cases and RPVI in 26 (36%) of 73 assessable cases. Patients with RPVI-positive lesions exhibited a significantly better overall survival (OS) than patients with RPVI-negative lymphoma, particularly among patients treated with high-dose methotrexate-based chemotherapy (3-year OS: 59 +/- 14% vs. 42 +/- 9%, P = 0.02). By contrast, the presence of TN did not demonstrate prognostic significance. Multivariate analysis confirmed an independent association between RPVI and survival. In conclusion, the presence of RPVI is independently associated with survival in PCNSL. This parameter can be easily and routinely assessed at diagnosis on histopathological specimens.

DNase I and micrococcal nuclease analysis of the tomato proteinase inhibitor I gene in chromatin.

The chromatin structure of the wound-inducible proteinase inhibitor I gene was investigated in nuclei from leaves of wounded and unwounded tomato plants. DNase I digestion of intact nuclei revealed that the inhibitor I chromatin structure was highly sensitive to the enzyme compared to the inactive ribosomal chromatin. This sensitivity was independent of wounding. Digestion of tomato nuclei with micrococcal nuclease, which produces a nucleosomal ladder from bulk chromatin in agarose gels, supported these observations. Micrococcal nuclease produced only a faint nucleosomal repeat superimposed on a smear for the coding region of the inhibitor I gene, whereas digestion of inactive ribosomal chromatin produced a well defined nucleosomal ladder. Two DNase I-hypersensitive sites were found in the promoter region of the inhibitor I gene. Both were present before and after wound induction. These two constitutive DNase I-hypersensitive sites may correspond to DNA regulatory regions of the gene. The combined results indicate the existence of an open chromatin conformation in the inhibitor I gene DNA region, present before gene induction by wounding.