Analysis of tropomyosin cDNAs isolated from skeletal and smooth muscle mRNA.

Several clones containing alpha tropomyosin sequences were isolated from cDNA libraries prepared from quail skeletal or smooth muscle RNA. All of these clones contain identical sequences coding for amino acids 81-257 of alpha skeletal muscle tropomyosin where they overlap, strongly indicating they are derived from the same gene. However, there are differences among these clones in sequences coding for the final 27 amino acids, as well as 3' untranslated sequences. In addition, S1 nuclease and Northern analyses indicate that coding sequences at the 5' end of the tropomyosin mRNA are also differentially expressed in smooth and skeletal muscle. These data point to the likelihood that differential splicing at both the 5' and 3' ends of a single tropomyosin gene results in the appearance of multiple tissue-specific transcripts

Sequence Requirements for Interaction of Human Herpesvirus 7 Origin Binding Protein with the Origin of Lytic Replication

As do human herpesvirus 6 variants A and B (HHV-6A and -6B), HHV-7 encodes a homolog of the alphaherpesvirus origin binding protein (OBP), which binds at sites in the origin of lytic replication (oriLyt) to initiate DNA replication. In this study, we sought to characterize the interaction of the HHV-7 OBP (OBP(H7)) with its cognate sites in the 600-bp HHV-7 oriLyt. We expressed the carboxyl-terminal domain of OBP(H7) and found that amino acids 484 to 787 of OBP(H7) were sufficient for DNA binding activity by electrophoretic mobility shift analysis. OBP(H7) has one high-affinity binding site (OBP-2) located on one flank of an AT-rich spacer element and a low-affinity site (OBP-1) on the other. This is in contrast to the HHV-6B OBP (OBP(H6B)), which binds with similar affinity to its two cognate OBP sites in the HHV-6B oriLyt. The minimal recognition element of the OBP-2 site was mapped to a 14-bp sequence. The OBP(H7) consensus recognition sequence of the 9-bp core, BRTYCWCCT (where B is a T, G, or C; R is a G or A; Y is a T or C; and W is a T or A), overlaps with the OBP(H6B) consensus YGWYCWCCY and establishes YCWCC as the roseolovirus OBP core recognition sequence. Heteroduplex analysis suggests that OBP(H7) interacts along one face of the DNA helix, with the major groove, as do OBP(H6B) and herpes simplex virus type 1 OBP. Together, these results illustrate both conserved and divergent DNA binding properties between OBP(H7) and OBP(H6B)