Hantaviruses are enveloped, negative-strand RNA viruses which can be lethal to humans, causing either a hemorrhagic fever with renal syndrome or a hantaviral pulmonary syndrome. The viral genomes consist of three RNA segments: the L segment encodes the viral polymerase, the M segment encodes the viral surface glycoproteins G1 and G2, and the S segment encodes the nucleocapsid (N) protein. The N protein is a 420-to 430-residue, 50-kDa protein which appears to direct hantavirus assembly, although mechanisms of N protein oligomerization, RNA encapsidation, budding, and release are poorly understood. We have undertaken a biochemical and genetic analysis of N protein oligomerization. Bacterially expressed N proteins were found by gradient fractionation to associate not only as large multimers or aggregates but also as dimers or trimers. Chemical cross-linking of hantavirus particles yielded N protein cross-link products with molecular masses of 140 to 150 kDa, consistent with the size of an N trimer. We also employed a genetic, yeast two-hybrid method for monitoring N protein interactions. Analyses showed that the C-terminal half of the N protein plus the N-terminal 40 residues permitted association with a full-length N protein fusion. These N-terminal 40 residues of seven different hantavirus strains were predicted to form trimeric coiled coils. Our results suggest that coiled-coil motifs contribute to N protein trimerization and that nucleocapsid protein trimers are hantavirus particle assembly intermediates. Hantaviruses, such as the Sin Nombre hantavirus (SNV) andProspect Hill virus (PHV), are members of the bunyavirus class of viruses (3,20,24). They are enveloped, negative-strand RNA viruses and carry three genomic RNA segments: the L segment, which encodes an RNA-dependent RNA polymerase; the M segment, which encodes envelope glycoproteins G1 and G2; and the S segment, which encodes the viral nucleocapsid (N) protein (24). Hantaviruses are of medical importance, because many of them cause either a hemorrhagic fever with renal syndrome or a hantaviral pulmonary syndrome, which is characterized by lung damage and cardiac dysfunction (25).Models for hantavirus replication at the cellular level have been based on direct experiments and by inference from work on other bunyaviruses. The general replication cycle starts with G1 and G2 binding to B3 integrins (7,8) or other cell surface receptors, followed by virus entry and uncoating. After entry, L protein-mediated primary transcription of mRNAs occurs in the cytoplasm, apparently using an orthomyxovirus-like capsnatching mechanism (4, 14). Following mRNA translation, transcription shifts from mRNA to cRNA and viral RNA synthesis, and ribonucleoprotein (RNP) structures are formed (4, 14, 24). The RNPs appear to be composed of viral RNAs, N proteins, and presumably L proteins and accumulate on the cytoplasmic sides of cellular membranes, possibly through interactions with the G1 and G2 proteins (9, 21). Evidence suggests that RNPs use microfilaments for transport to ...

Although most patients with chronic myeloid leukemia (CML) treated with imatinib mesylate achieve a complete cytogenetic response (CCR), some patients will relapse. To determine the potential of real-time quantitative BCR-ABL reverse transcriptase-polymerase chain reaction (RT-PCR) to predict the duration of continued CCR, we monitored 85 patients treated with imatinib mesylate who achieved a CCR. With a median follow-up of 13 months after CCR (29 months after imatinib mesylate; median 6 RQ-PCR assays), 23 patients (27%) had disease progression (predominantly loss of CCR). Compared with the median baseline level of BCR-ABL mRNA, 42% of patients achieved at least a 2-log molecular response at the time of first reaching CCR. Failure to achieve a 2-log response at the time of CCR was an independent predictive marker of subsequent progressionfree survival (hazard ratio ‫؍‬ 5.8; 95% CI, 1.7-20; P ‫؍‬ .005). After CCR, BCR-ABL mRNA levels progressively declined for at least the next 15 months, and 42 patients (49%) ultimately achieved at least a 3-log reduction in BCR-ABL mRNA. Patients failing to achieve this 3-log response, at any time during therapy, had significantly shorter progression-free survival (hazard ratio ‫؍‬ 8.1; 95% CI, 3.1-22; P < .001). The achievement of either a 2-log molecular response at the time of CCR or a 3-log response anytime thereafter is a significant and independent prognostic marker of subsequent progressionfree survival. (Blood. 2006;107:4250-4256)

Strains of the budding yeast, Saccharomyces cerevisiae, may contain one or more cytoplasmic viruses with double‐stranded RNA (dsRNA) genomes. The killer phenomenon in yeast, in which one cell secretes a killer toxin that is lethal to another cell, is dependent upon the presence of the L‐A and M1 dsRNA viruses. The L‐A viral genome encodes proteins for the viral capsid, and for synthesis and encapsidation of single‐stranded RNA replication cycle intermediates. The M1 virus depends upon the L‐A‐encoded proteins for its capsid and for the replication of its killer‐toxin‐encoding genome. A full‐length cDNA clone of an M1 genome has been made from a single dsRNA molecule and shown to encode functional killer and killer‐immunity functions. The sequence of the clone indicates minor differences from previously published sequences of parts of the M1 genome and of the complete genome of S14 (an internal deletion derivative of M1) but no unreported amino acid variants and no changes in putative secondary structures of the single‐stranded RNA. A 118‐nucleotide contiguous segment of the M1 genome has not previously been reported; 92 of those nucleotides comprise a segment of A nucleotides in the AU‐rich bubble that follows the toxin‐encoding reading frame. The GenBank Accession Number for the sequence is U78817; the locus is SCU78817. © 1997 John Wiley & Sons, Ltd.