Structure of the macronuclear polyubiquitin gene in Euplotes.

The hypotrichous ciliate, Euplotes eurystomus, contains both a transcriptionally inactive micronucleus (MIC) and a transcriptionally active macronucleus (MAC) in the same cell. MAC DNA is small (0.5-20 kb), linear and highly amplified. Each DNA fragment consists of two telomeres, a single coding region, and the necessary control elements to regulate gene transcription and replication. The polyubiquitin gene consists of 898 bp, plus 28 bp of double-stranded and 14 bases of single-stranded DNA of the telomeric repeat G4T4 at each end. The coding region exists as three copies of the ubiquitin gene (690 bp) fused in a head-to-tail arrangement as in other organisms. The stop codon is TAA, as in other Euplotes genes, and is not the rare glutamine codon used in most other ciliates. The 3' nontranslated region contains two presumptive poly(A) addition sites; the 5' nontranslated region possesses two putative TATA boxes, several imperfect direct and inverted repeats, and a possible origin of replication. Nucleosome positioning studies reveal four tightly packed nucleosomes and a non-nucleosomal area containing the probable 5' control region as well as part of the coding region. The 5' area does not contain any DNAse I hypersensitive sites. Although the telomeres are protected from exonuclease digestion, they are not as well protected as Oxytricha telomeres against endonucleases and cleavage by methidium propyl Fe2+ EDTA.

The 5S RNA gene minichromosome of Euplotes.

The macronucleus of the ciliated protozoan Euplotes eurystomus contains about 10(6) copies of a single type of 5S ribosomal RNA gene. This 5S gene DNA is only 930 bp long, is flanked by telomeres, and contains a single coding region of 120 bp which serves as a template for transcription in vivo and in vitro. The 5S gene minichromatin possesses four positioned nucleosomes and hypersensitive cleavage sites in the telomeric regions.

Subfractionation of soluble macronuclear chromatin and enrichment of specific genes as chromatin from Euplotes eurystomus.

Euplotes eurystomus is a hypotrichous ciliated protozoan possessing within one cytoplasm a transcriptionally-inactive micronucleus with chromosomal-size DNA and a transcriptionally active macronucleus with "gene-size" DNA fragments. The chromatin in the macronucleus can be isolated in a soluble form without prior treatment by nucleases. In this study, macronuclear, soluble chromatin was subfractionated using isokinetic sucrose density gradient ultracentrifugation in a buffer consisting of 50 mM NaCl, 1 mM Na2 EDTA, 1 mM TEA HCl, pH 7.0, 0.1 mM TLCK and 0.1 mM PMSF. Fractions were collected and analyzed by DNA and protein gel electrophoresis, dot blot hybridization with specific gene probes, and modified Miller chromatin spreads. Analysis of the chromatin spreads showed that the sizes of the chromatin fragments in the various fractions correlate with the DNA size of the fragments. When dot blots of the fractions were hybridized with 5S rRNA, tubulin and rRNA gene probes we obtained about a 6 to 14-fold enrichment of hybridizable sequences in individual fractions. There appear to be differences in the non-histones present on each fraction as well as some overall similarities in histone and non-histone proteins.

46,XY,i(21q) identified by maternal serum screening.

Maternal serum screening for the detection of fetal Down syndrome has become widespread. Prenatal detection of fetal Down syndrome has important implications not only for management of the current pregnancy, but also for recurrence risk counseling for future pregnancies. We report a case of fetal Down syndrome due to an isochromosome 21q detected after maternal serum screening using alpha-fetoprotein and human chorionic gonadotropin indicated an increased risk for fetal Down syndrome in a 19-year-old pregnant woman. This confirms that maternal serum screening can detect fetal Down syndrome due to rare chromosome rearrangements and illustrates the importance of cytogenetic studies for provision of appropriate genetic counseling.

X-ray diffraction analysis of crystals containing twofold symmetric nucleosome core particles.

Nucleosome core particles containing a DNA palindrome and purified chicken erythrocyte histone octamer have been reconstituted and crystallized. The dyad symmetry of the palindrome extends the dyad symmetry of the histone octamer to result in a twofold symmetric particle. This ensures that the structure determined by X-ray diffraction will yield a true representation of the DNA strand rather than the twofold averaged structure which would result from using a non-palindromic DNA sequence. The crystals provide isotropic diffraction to 3.2 A with observed reflections extending to d spacings of about 2.8 A using a rotating-anode Cu Kalpha X-ray source. Although the DNA palindrome is a factor contributing to the quality of the diffraction data, another significant factor is an improved preparative technique which enriches for correctly phased nucleosome core particles.

All-trans-retinoic acid-induced myositis: a description of two patients.

All-trans-retinoic acid (ATRA) induces complete clinical remissions in a high proportion of patients with acute promyelocytic leukemia and has become the standard induction therapy. Its use as a single agent results in short-lived remissions; thus, cytotoxic drugs are used for "consolidation" therapy. Side effects reported during treatment with ATRA include retinoic acid syndrome and Sweet's syndrome. Sweet's syndrome has been associated with acute myelogenous leukemia at presentation, but only two cases of Sweet's syndrome involving the musculoskeletal system in patients treated with ATRA have been described. We describe two additional patients with acute promyelocytic leukemia who had unexplained fever and myalgias (cutaneous lesions in one patient) during induction therapy with ATRA. Radiologic findings were similar to those in previously reported ATRA-associated Sweet's syndrome of the musculoskeletal system. The clinical course was characterized by a rapid resolution of the symptoms during treatment with dexamethasone. Recognition of the syndrome is important, especially considering the rapid resolution of symptoms after early institution of therapy with corticosteroids.