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A complementary DNA library was constructed from mRNA purified from asexual blood forms of Plasmodium falciparum. Among the members of this library we have identified a plasmid (pMC31‐1) coding for a polypeptide exposed at the surface of merozoites, the invasive stage of the asexual cycle. This plasmid was identified by direct expression using both polyclonal and monoclonal antibodies specific for a schizont polypeptide of 200 kd which has been shown to be processed to an 83‐kd polypeptide expressed at the surface of merozoites. The cDNA portion of the pMC31‐1 plasmid hybridizes with DNA from three isolates of P. falciparum. Antisera raised against extracts of Escherichia coli harbouring pMC31‐1 react with surface and internal structures of schizonts and with the surface of merozoites from all the isolates of P. falciparum examined. These results suggest that plasmid pMC31‐1 encodes an antigen of value for the development of a vaccine against malaria.

A high level of plasma fibrinogen has been shown to be an important risk factor for myocardial infarction and stroke. Thus, we were prompted to investigate regulation of human fibrinogen biosynthesis, a process wherein expression of the B beta-chain of fibrinogen appears to be rate-limiting for fibrinogen secretion. Using electrophoretic mobility shift assays with synthetic probes representing portions of the human B beta-fibrinogen promoter, we have defined several elements that bind distinct classes of transcription factors present in human hepatoma cell nuclear extracts. The contribution of each element to promoter activity was demonstrated in transfection experiments using promoter-chloramphenicol acetyltransferase constructs and human hepatoma cells. Our observations indicate that two distinct sequence elements are required for maximal induction of transcription by interleukin-6. One of these sequences is an IL-6-RE core element similar to that reported for the rat alpha 2-macroglobulin promoter and the other is a binding site for the C/EBP family of transcription factors. We also report two additional elements, one negative- and one positive-acting, that bind novel sequence-specific factors.