RNA sequencing steps toward the first line

• DNA is the sequence that codes for proteins.
• Messenger RNA is transcribed from the DNA sequence of genes and translated into protein.
• It can be difficult to predict how a change in the DNA sequence will affect messenger RNA and protein quantity and quality.
• DNA translocation changes can cause the joining of sequences from two different genes or different parts of the same gene.
• DNA sequencing is often used clinically to predict how DNA changes might affect proteins.
• Alternatively, RNA sequencing can be used as a more direct measure of the effect of DNA changes on the protein products.
• This sequencing is important for identifying changes in cancer that may indicate response to targeted therapy, prognosis, or diagnosis.

     

Rotation of the head of the 30S ribosomal subunit during mRNA translocation

Elongation factor-G–catalyzed translocation of mRNA and tRNAs during protein synthesis involves large-scale conformational changes in the ribosome. Formation of hybrid-state intermediates is coupled to counterclockwise (forward) rotation of the body of the 30S subunit. Recent structural studies implicate intrasubunit rotation of the 30S head in translocation. Here, we observe rotation of the head during translocation in real time using ensemble stopped-flow FRET with ribosomes containing fluorescent probes attached to specific positions in the head and body of the 30S subunit. Our results allow ordering of the rates of movement of the 30S subunit body and head during translocation: body forward > head forward > head reverse ≥ body reverse. The rate of quenching of pyrene-labeled mRNA is consistent with coupling of mRNA translocation to head rotation.     

Cotranslational folding of membrane proteins probed by arrest-peptide–mediated force measurements

Polytopic membrane proteins are inserted cotranslationally into target membranes by ribosome–translocon complexes. It is, however, unclear when during the insertion process specific interactions between the transmembrane helices start to form. Here, we use a recently developed in vivo technique to measure pulling forces acting on transmembrane helices during their cotranslational insertion into the inner membrane of Escherichia coli to study the earliest steps of tertiary folding of five polytopic membrane proteins. We find that interactions between residues in a C-terminally located transmembrane helix and in more N-terminally located helices can be detected already at the point when the C-terminal helix partitions from the translocon into the membrane. Our findings pinpoint the earliest steps of tertiary structure formation and open up possibilities to study the cotranslational folding of polytopic membrane proteins.     

Unbalanced 1;7 translocation and therapy-induced hematologic disorders: a possible relationship

An identical chromosome abnormality, which appears to be derived from a 1;7 translocation [+der(1),t(1;7)(p11;p11)], was observed in the bone marrow of 12 patients with various hematologic disorders at the Mayo Clinic from 1980 to 1984. At the time of cytogenetic evaluation, nine of the patients had either a myeloproliferative disorder or a myelodysplastic syndrome, one had an acute leukemia, and two had treated multiple myeloma with no morphologic evidence of evolving myeloproliferative disease. Of the 11 patients for whom information about previous therapy was available, seven had a history of exposure to chemotherapy for a previous malignant disorder; we were unable to establish whether the remaining patient had had prior treatment. This study suggests a possible relationship between +der(1),t(1;7)(p11;p11) and some treatment-induced hematologic disorders. Such chromosome abnormalities may be the result of a reciprocal chromatid translocation and adjacent I segregation of a quadriradial configuration in metaphase.     

Can t(8;21) oligoblastic leukemia be called a myelodysplastic syndrome?

The new World Health Organization (WHO) classification of hematologic malignancies has incorporated t(8;21) myelodysplastic syndromes (MDS) according to the French-American-British classification into the category of acute myeloid leukemia (AML) with t(8;21)(q22;q22), while our knowledge about clinicopathological features of t(8;21) oligoblastic leukemia is still limited. We present our experience with 12 patients meeting the FAB diagnostic criteria of MDS and having t(8;21), who were compared to 43 t(8;21) AML patients. The MDS and AML patients shared most hematomorphologic, immunophenotypic, and clinical features, whereas the differences lay along myeloid maturation. The MDS patients had higher percentages of circulating neutrophils and marrow myeloid cells beyond promyelocytes than the AML patients. The incidence of Auer rods in mature neutrophils in MDS was significantly higher than that in AML, and furthermore, the neutrophils in MDS more commonly contain t(8;21) than in AML. Our findings support the rationale for the WHO classification, and future studies on large patient populations should help clarify whether the spontaneous differentiation potential could be actively associated with a hematological manifestation of t(8;21) leukemias.