To identify proteins that interact with Jun or Fos we have used the protein interaction cloning system developed by S. Fields and O.-K. Song [(1989) Nature (London) 340, [245][246] to clone mammalian cDNAs encoding polypeptides that interact with the dimerization and DNA-binding motif (bZIP; basic domain leucine zipper motif) ofJun. For this purpose, yeast cells lacking GAL4 activity but expressing a GAL4 DNA-binding domain-Jun bZIP fusion protein were transformed with a mouse embryo cDNA plasmid library in which the cDNA was joined to a gene segment encoding the GAL4 transcriptional activation domain. Several transformants exhibiting GAL4 activity were identified and shown to harbor plasmids encoding polypeptides predicted to form coiled-coil structures with Jun and/or Fos. One of these is a bZIP protein of the ATF/CREB protein family-probably the murine homolog of TAXREB67. Two others encode polypeptides with predicted potential to form coiled-coil structures, and seven other isolates encode segments of a-or f-tropomyosin, classical coiled-coil proteins. The tropomyosin polypeptides were found to interact in the yeast assay system with the bZIP region of Jun but not with the bZIP region of Fos. Our results illustrate the range of protein interaction cloning for discovering proteins that bind to a given target polypeptide.Jun and Fos are sequence-specific DNA-binding proteins that regulate transcription. Each protein has a bipartite DNAbinding domain [bZIP; basic domain leucine zipper motif (1)] consisting of an amphipathic helix that mediates dimerization through formation of a short coiled-coil structure (2), termed the "leucine zipper" (3), and an adjacent basic region that contacts DNA (4-6). Dimerization of monomers in a parallel orientation positions each basic region to interact with a half site of the DNA target sequence. In principle, a given bZIP transcription factor could interact with a variety of bZIP proteins with compatible amphipathic helices, yielding dimers with different DNA-binding and transcriptional properties (for review, see ref. 7). In the case of the known members of the Jun and Fos families, all pairwise combinations capable of forming dimers bind to the same dyad symmetric core sequence (8) (for reviews, see refs. 9 and 10), but their transcriptional properties often vary (11, 12). Moreover, the transcriptional activities ofJun can be modulated by interactions with other proteins, such as the glucocorticoid receptor (13-15), the inhibitory protein IP-1 (16), and a cell-specific inhibitor (17).The goal of the present study is to identify additional mammalian proteins that interact with Jun or Fos, some of which may form DNA-binding dimers with activities different from those of Jun-Fos heterodimers. For this purpose, we have used a yeast genetic system described by Fields and coworkers (18,19) in which expression of a GALJ-lacZ reporter gene under the control ofa GAL4-activated promotor depends on reconstitution of GAL4 activity via proteinprotein interaction. This is acc...

Breast reconstruction using the lower abdominal free superficial inferior epigastric artery (SIEA) flap has the potential to virtually eliminate abdominal donor-site morbidity because the rectus abdominis fascia and muscle are not incised or excised. However, despite its advantages, the free SIEA flap for breast reconstruction is rarely used. A prospective study was conducted of the reliability and outcomes of the use of SIEA flaps for breast reconstruction compared with transverse rectus abdominis musculocutaneous (TRAM) and deep inferior epigastric perforator (DIEP) flaps. Breast reconstruction with an SIEA flap was attempted in 47 consecutive free autologous tissue breast reconstructions between August of 2001 and November of 2002. The average patient age was 49 years, and the average body mass index was 27 kg/m. The SIEA flap was used in 14 (30 percent) of these breast reconstructions in 12 patients. An SIEA flap was not used in the remaining 33 cases because the SIEA was absent or was deemed too small. The mean superficial inferior epigastric vessel pedicle length was approximately 7 cm. The internal mammary vessels were used as recipients in all SIEA flap cases so that the flap could be positioned sufficiently medially on the chest wall. The average hospital stay was significantly shorter for patients who underwent unilateral breast reconstruction with SIEA flaps than it was for those who underwent reconstruction with TRAM or DIEP flaps. Of the 47 free flaps, one SIEA flap was lost because of arterial thrombosis. Medium-size and large breasts were reconstructed with hemi-lower abdominal SIEA flaps, with aesthetic results similar to those obtained with TRAM and DIEP flaps. The free SIEA flap is an attractive option for autologous tissue breast reconstruction. Harvest of this flap does not injure the anterior rectus fascia or underlying rectus abdominis muscle. This can potentially eliminate abdominal donor-site complications such as bulge and hernia formation, and decrease weakness, discomfort, and hospital stay compared with TRAM and DIEP flaps. The disadvantages of an SIEA flap are a smaller pedicle diameter and shorter pedicle length than TRAM and DIEP flaps and the absence or inadequacy of an arterial pedicle in most patients. Nevertheless, in selected patients, the SIEA flap offers advantages over the TRAM and DIEP flaps for breast reconstruction.

The implantable Doppler probe is a sensitive method for postoperative monitoring of free flaps but is prone to false-positive signals. The use of color duplex sonography to confirm implantable Doppler probe findings may avert unnecessary surgical exploration, thereby improving postoperative monitoring of free flaps.