3 DIFFERENT CDNAS ENCODING MOUSE D-FACTOR LIF RECEPTOR/

Three cDNAs for mouse differentiation-stimulating factor (D-factor)/le ukemia inhibitory factor (LIF) receptor were isolated from a cDNA libr ary prepared from the liver of a pregnant mouse. A probe for screening was prepared by the RT-PCR method using human cDNA sequences as prime rs. The mouse D-factor receptor cDNA encoded 1,092 amino acids, which had a marked homology with the human counterpart and consisted of sign al sequence, extracellular, transmembrane, and cytoplasmic domains. Th e WSXWS motif found in members of the cytokine receptor family was als o present in the extracellular domain of the mouse D-factor receptor. A second form of cDNA that had a 501 bp insertion was isolated. The in sertion introduced a stop codon so that the mRNA encoded the soluble r eceptor lacking transmembrane and intracellular domains. Because the i nsertion contained polyadenylation signals, two different sizes of mRN A encoding the soluble receptor were produced, depending on whether or not it utilized these signals. Transcripts utilizing these signals we re 2.6-3 kb in size, and were very abundantly expressed in the liver. Transcripts that did not use these signals were longer than 5 kb and o f similar size to the mRNA for the cellular receptor.